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	$166.57	11.155%	$185.1509	$185.15	$185.15	$185.20
Purchase #2	$191.38	11.240%	$212.8911	$212.89	$212.90	$212.90
Purchase #3	$85.98	7.287%	$92.2454	$92.25	$92.25	$92.20
Purchase #4	$181.43	5.181%	$190.8299	$190.83	$190.85	$190.80
Purchase #5	$128.78	10.503%	$142.3058	$142.31	$142.30	$142.30
Purchase #6	$110.88	8.711%	$120.5388	$120.54	$120.55	$120.50
Purchase #7	$236.97	6.624%	$252.6669	$252.67	$252.65	$252.70
7 purchase totals =	$1,101.99		$1,196.6288	$1,196.64	$1,196.65	$1,196.60