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	$236.50	11.768%	$264.3313	$264.33	$264.35	$264.30
Purchase #2	$214.65	10.174%	$236.4885	$236.49	$236.50	$236.50
Purchase #3	$9.34	9.453%	$10.2229	$10.22	$10.20	$10.20
Purchase #4	$100.47	3.433%	$103.9191	$103.92	$103.90	$103.90
Purchase #5	$120.34	5.449%	$126.8973	$126.90	$126.90	$126.90
Purchase #6	$29.59	9.497%	$32.4002	$32.40	$32.40	$32.40
Purchase #7	$42.52	11.739%	$47.5114	$47.51	$47.50	$47.50
7 purchase totals =	$753.41		$821.7707	$821.77	$821.75	$821.70