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	$33.58	12.730%	$37.8547	$37.85	$37.85	$37.90
Purchase #2	$211.44	10.609%	$233.8717	$233.87	$233.85	$233.90
Purchase #3	$181.71	4.730%	$190.3049	$190.30	$190.30	$190.30
Purchase #4	$161.33	11.168%	$179.3473	$179.35	$179.35	$179.30
Purchase #5	$114.44	12.816%	$129.1066	$129.11	$129.10	$129.10
Purchase #6	$56.70	5.345%	$59.7306	$59.73	$59.75	$59.70
Purchase #7	$102.61	11.153%	$114.0541	$114.05	$114.05	$114.10
7 purchase totals =	$861.81		$944.2699	$944.26	$944.25	$944.30