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	$180.30	5.593%	$190.3842	$190.38	$190.40	$190.40
Purchase #2	$145.47	3.424%	$150.4509	$150.45	$150.45	$150.50
Purchase #3	$136.74	6.428%	$145.5296	$145.53	$145.55	$145.50
Purchase #4	$40.76	11.712%	$45.5338	$45.53	$45.55	$45.50
Purchase #5	$48.85	7.118%	$52.3271	$52.33	$52.35	$52.30
Purchase #6	$54.49	11.647%	$60.8365	$60.84	$60.85	$60.80
Purchase #7	$94.40	7.707%	$101.6754	$101.68	$101.70	$101.70
7 purchase totals =	$701.01		$746.7375	$746.74	$746.85	$746.70