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	$130.35	11.675%	$145.5684	$145.57	$145.55	$145.60
Purchase #2	$61.36	9.395%	$67.1248	$67.12	$67.10	$67.10
Purchase #3	$59.82	9.474%	$65.4873	$65.49	$65.50	$65.50
Purchase #4	$135.64	11.612%	$151.3905	$151.39	$151.40	$151.40
Purchase #5	$94.82	9.406%	$103.7388	$103.74	$103.75	$103.70
Purchase #6	$141.55	10.469%	$156.3689	$156.37	$156.35	$156.40
Purchase #7	$103.63	13.607%	$117.7309	$117.73	$117.75	$117.70
7 purchase totals =	$727.17		$807.4096	$807.41	$807.40	$807.40