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	$144.67	10.454%	$159.7938	$159.79	$159.80	$159.80
Purchase #2	$174.68	12.367%	$196.2827	$196.28	$196.30	$196.30
Purchase #3	$18.83	9.419%	$20.6036	$20.60	$20.60	$20.60
Purchase #4	$246.26	11.819%	$275.3655	$275.37	$275.35	$275.40
Purchase #5	$59.57	13.586%	$67.6632	$67.66	$67.65	$67.70
Purchase #6	$166.29	8.426%	$180.3016	$180.30	$180.30	$180.30
Purchase #7	$45.75	13.144%	$51.7634	$51.76	$51.75	$51.80
7 purchase totals =	$856.05		$951.7738	$951.76	$951.75	$951.90