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	$229.43	6.401%	$244.1158	$244.12	$244.10	$244.10
Purchase #2	$105.72	4.588%	$110.5704	$110.57	$110.55	$110.60
Purchase #3	$9.26	11.678%	$10.3414	$10.34	$10.35	$10.30
Purchase #4	$55.56	6.294%	$59.0569	$59.06	$59.05	$59.10
Purchase #5	$53.33	5.159%	$56.0813	$56.08	$56.10	$56.10
Purchase #6	$123.92	6.649%	$132.1594	$132.16	$132.15	$132.20
Purchase #7	$131.93	8.263%	$142.8314	$142.83	$142.85	$142.80
7 purchase totals =	$709.15		$755.1566	$755.16	$755.15	$755.20