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	$49.27	7.338%	$52.8854	$52.89	$52.90	$52.90
Purchase #2	$26.62	3.745%	$27.6169	$27.62	$27.60	$27.60
Purchase #3	$217.66	12.175%	$244.1601	$244.16	$244.15	$244.20
Purchase #4	$215.32	3.335%	$222.5009	$222.50	$222.50	$222.50
Purchase #5	$77.84	6.770%	$83.1098	$83.11	$83.10	$83.10
Purchase #6	$236.39	13.801%	$269.0142	$269.01	$269.00	$269.00
Purchase #7	$85.41	11.388%	$95.1365	$95.14	$95.15	$95.10
7 purchase totals =	$908.51		$994.4238	$994.43	$994.40	$994.40