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	$70.68	5.108%	$74.2903	$74.29	$74.30	$74.30
Purchase #2	$107.35	3.868%	$111.5023	$111.50	$111.50	$111.50
Purchase #3	$65.38	11.477%	$72.8837	$72.88	$72.90	$72.90
Purchase #4	$235.29	9.680%	$258.0661	$258.07	$258.05	$258.10
Purchase #5	$206.72	8.305%	$223.8881	$223.89	$223.90	$223.90
Purchase #6	$108.67	9.805%	$119.3251	$119.33	$119.35	$119.30
Purchase #7	$154.59	6.860%	$165.1949	$165.19	$165.20	$165.20
7 purchase totals =	$948.68		$1,025.1505	$1,025.15	$1,025.20	$1,025.20