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	$152.77	9.690%	$167.5734	$167.57	$167.55	$167.60
Purchase #2	$72.44	13.831%	$82.4592	$82.46	$82.45	$82.50
Purchase #3	$63.81	11.766%	$71.3179	$71.32	$71.30	$71.30
Purchase #4	$50.53	5.224%	$53.1697	$53.17	$53.15	$53.20
Purchase #5	$122.73	6.489%	$130.6939	$130.69	$130.70	$130.70
Purchase #6	$18.61	6.603%	$19.8388	$19.84	$19.85	$19.80
Purchase #7	$29.90	13.604%	$33.9676	$33.97	$33.95	$34.00
7 purchase totals =	$510.79		$559.0205	$559.02	$558.95	$559.10