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	$141.66	4.379%	$147.8633	$147.86	$147.85	$147.90
Purchase #2	$43.86	4.616%	$45.8846	$45.88	$45.90	$45.90
Purchase #3	$16.68	13.281%	$18.8953	$18.90	$18.90	$18.90
Purchase #4	$230.47	5.772%	$243.7727	$243.77	$243.75	$243.80
Purchase #5	$236.67	7.552%	$254.5433	$254.54	$254.55	$254.50
Purchase #6	$197.67	13.208%	$223.7783	$223.78	$223.80	$223.80
Purchase #7	$192.34	11.621%	$214.6918	$214.69	$214.70	$214.70
7 purchase totals =	$1,059.35		$1,149.4293	$1,149.42	$1,149.45	$1,149.50