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	$214.62	3.586%	$222.3163	$222.32	$222.30	$222.30
Purchase #2	$166.64	13.805%	$189.6447	$189.64	$189.65	$189.60
Purchase #3	$182.86	4.508%	$191.1033	$191.10	$191.10	$191.10
Purchase #4	$55.39	10.480%	$61.1949	$61.19	$61.20	$61.20
Purchase #5	$145.85	10.352%	$160.9484	$160.95	$160.95	$160.90
Purchase #6	$86.55	6.533%	$92.2043	$92.20	$92.20	$92.20
Purchase #7	$154.30	11.649%	$172.2744	$172.27	$172.25	$172.30
7 purchase totals =	$1,006.21		$1,089.6863	$1,089.67	$1,089.65	$1,089.60