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	$37.40	12.113%	$41.9303	$41.93	$41.95	$41.90
Purchase #2	$53.30	4.341%	$55.6138	$55.61	$55.60	$55.60
Purchase #3	$82.64	4.662%	$86.4927	$86.49	$86.50	$86.50
Purchase #4	$38.32	3.760%	$39.7608	$39.76	$39.75	$39.80
Purchase #5	$211.46	5.375%	$222.826	$222.83	$222.85	$222.80
Purchase #6	$250.30	8.840%	$272.4265	$272.43	$272.45	$272.40
Purchase #7	$166.39	9.539%	$182.2619	$182.26	$182.25	$182.30
7 purchase totals =	$839.81		$901.3120	$901.31	$901.35	$901.30