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	$203.73	10.240%	$224.592	$224.59	$224.60	$224.60
Purchase #2	$38.72	12.103%	$43.4063	$43.41	$43.40	$43.40
Purchase #3	$93.87	6.542%	$100.011	$100.01	$100.00	$100.00
Purchase #4	$234.98	7.136%	$251.7482	$251.75	$251.75	$251.70
Purchase #5	$97.77	11.663%	$109.1729	$109.17	$109.15	$109.20
Purchase #6	$242.69	9.504%	$265.7553	$265.76	$265.75	$265.80
Purchase #7	$139.80	11.657%	$156.0965	$156.10	$156.10	$156.10
7 purchase totals =	$1,051.56		$1,150.7822	$1,150.79	$1,150.75	$1,150.80