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	$27.73	3.784%	$28.7793	$28.78	$28.80	$28.80
Purchase #2	$74.71	6.231%	$79.3652	$79.37	$79.35	$79.40
Purchase #3	$247.34	11.452%	$275.6654	$275.67	$275.65	$275.70
Purchase #4	$89.45	3.371%	$92.4654	$92.47	$92.45	$92.50
Purchase #5	$174.50	12.714%	$196.6859	$196.69	$196.70	$196.70
Purchase #6	$223.98	8.317%	$242.6084	$242.61	$242.60	$242.60
Purchase #7	$114.92	9.816%	$126.2005	$126.20	$126.20	$126.20
7 purchase totals =	$952.63		$1,041.7701	$1,041.79	$1,041.75	$1,041.90