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	$6.79	6.721%	$7.2464	$7.25	$7.25	$7.20
Purchase #2	$117.59	13.148%	$133.0507	$133.05	$133.05	$133.10
Purchase #3	$225.72	13.698%	$256.6391	$256.64	$256.65	$256.60
Purchase #4	$161.64	7.119%	$173.1472	$173.15	$173.15	$173.10
Purchase #5	$95.92	4.528%	$100.2633	$100.26	$100.25	$100.30
Purchase #6	$232.85	7.678%	$250.7282	$250.73	$250.75	$250.70
Purchase #7	$167.86	13.437%	$190.4153	$190.42	$190.40	$190.40
7 purchase totals =	$1,008.37		$1,111.4902	$1,111.50	$1,111.50	$1,111.40