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	$227.38	8.710%	$247.1848	$247.18	$247.20	$247.20
Purchase #2	$64.79	11.848%	$72.4663	$72.47	$72.45	$72.50
Purchase #3	$125.29	5.212%	$131.8201	$131.82	$131.80	$131.80
Purchase #4	$225.67	7.808%	$243.2903	$243.29	$243.30	$243.30
Purchase #5	$198.56	7.142%	$212.7412	$212.74	$212.75	$212.70
Purchase #6	$90.54	9.831%	$99.441	$99.44	$99.45	$99.40
Purchase #7	$107.31	8.425%	$116.3509	$116.35	$116.35	$116.40
7 purchase totals =	$1,039.54		$1,123.2946	$1,123.29	$1,123.30	$1,123.30