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	$45.57	6.277%	$48.4304	$48.43	$48.45	$48.40
Purchase #2	$142.78	13.576%	$162.1638	$162.16	$162.15	$162.20
Purchase #3	$90.88	10.357%	$100.2924	$100.29	$100.30	$100.30
Purchase #4	$88.28	9.718%	$96.8591	$96.86	$96.85	$96.90
Purchase #5	$237.34	11.298%	$264.1547	$264.15	$264.15	$264.20
Purchase #6	$204.67	4.817%	$214.529	$214.53	$214.55	$214.50
Purchase #7	$113.51	10.292%	$125.1924	$125.19	$125.20	$125.20
7 purchase totals =	$923.03		$1,011.6218	$1,011.61	$1,011.65	$1,011.70