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	$166.74	5.185%	$175.3855	$175.39	$175.40	$175.40
Purchase #2	$120.66	3.753%	$125.1884	$125.19	$125.20	$125.20
Purchase #3	$72.27	8.424%	$78.358	$78.36	$78.35	$78.40
Purchase #4	$191.82	4.213%	$199.9014	$199.90	$199.90	$199.90
Purchase #5	$171.78	11.388%	$191.3423	$191.34	$191.35	$191.30
Purchase #6	$163.65	13.230%	$185.3009	$185.30	$185.30	$185.30
Purchase #7	$160.47	4.592%	$167.8388	$167.84	$167.85	$167.80
7 purchase totals =	$1,047.39		$1,123.3153	$1,123.32	$1,123.35	$1,123.30