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	$156.26	9.635%	$171.3157	$171.32	$171.30	$171.30
Purchase #2	$41.49	11.593%	$46.2999	$46.30	$46.30	$46.30
Purchase #3	$72.54	12.702%	$81.754	$81.75	$81.75	$81.80
Purchase #4	$7.73	3.111%	$7.9705	$7.97	$7.95	$8.00
Purchase #5	$134.85	5.731%	$142.5783	$142.58	$142.60	$142.60
Purchase #6	$136.41	11.112%	$151.5679	$151.57	$151.55	$151.60
Purchase #7	$80.83	11.145%	$89.8385	$89.84	$89.85	$89.80
7 purchase totals =	$630.11		$691.3248	$691.33	$691.30	$691.40