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	$46.50	11.263%	$51.7373	$51.74	$51.75	$51.70
Purchase #2	$208.51	12.552%	$234.6822	$234.68	$234.70	$234.70
Purchase #3	$196.81	8.339%	$213.222	$213.22	$213.20	$213.20
Purchase #4	$85.74	7.861%	$92.48	$92.48	$92.50	$92.50
Purchase #5	$69.30	3.390%	$71.6493	$71.65	$71.65	$71.60
Purchase #6	$36.86	9.279%	$40.2802	$40.28	$40.30	$40.30
Purchase #7	$39.76	7.637%	$42.7965	$42.80	$42.80	$42.80
7 purchase totals =	$683.48		$746.8475	$746.85	$746.90	$746.80