Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$139.80	11.607%	$156.0266	$156.03	$156.05	$156.00
Purchase #2	$150.73	12.296%	$169.2638	$169.26	$169.25	$169.30
Purchase #3	$208.63	3.346%	$215.6108	$215.61	$215.60	$215.60
Purchase #4	$129.31	7.732%	$139.3082	$139.31	$139.30	$139.30
Purchase #5	$176.36	6.406%	$187.6576	$187.66	$187.65	$187.70
Purchase #6	$97.41	6.668%	$103.9053	$103.91	$103.90	$103.90
Purchase #7	$149.98	3.658%	$155.4663	$155.47	$155.45	$155.50
7 purchase totals =	$1,052.22		$1,127.2386	$1,127.25	$1,127.20	$1,127.30