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	$200.25	11.543%	$223.3649	$223.36	$223.35	$223.40
Purchase #2	$134.94	3.496%	$139.6575	$139.66	$139.65	$139.70
Purchase #3	$103.61	12.822%	$116.8949	$116.89	$116.90	$116.90
Purchase #4	$246.90	12.418%	$277.56	$277.56	$277.55	$277.60
Purchase #5	$160.40	4.507%	$167.6292	$167.63	$167.65	$167.60
Purchase #6	$234.84	9.394%	$256.9009	$256.90	$256.90	$256.90
Purchase #7	$166.46	5.828%	$176.1613	$176.16	$176.15	$176.20
7 purchase totals =	$1,247.40		$1,358.1687	$1,358.16	$1,358.15	$1,358.30