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	$245.82	9.388%	$268.8976	$268.90	$268.90	$268.90
Purchase #2	$229.98	9.268%	$251.2945	$251.29	$251.30	$251.30
Purchase #3	$42.25	13.121%	$47.7936	$47.79	$47.80	$47.80
Purchase #4	$34.52	3.119%	$35.5967	$35.60	$35.60	$35.60
Purchase #5	$224.39	13.834%	$255.4321	$255.43	$255.45	$255.40
Purchase #6	$212.63	11.172%	$236.385	$236.39	$236.40	$236.40
Purchase #7	$82.57	10.163%	$90.9616	$90.96	$90.95	$91.00
7 purchase totals =	$1,072.16		$1,186.3611	$1,186.36	$1,186.40	$1,186.40