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	$125.95	3.744%	$130.6656	$130.67	$130.65	$130.70
Purchase #2	$78.78	13.193%	$89.1734	$89.17	$89.15	$89.20
Purchase #3	$26.96	11.741%	$30.1254	$30.13	$30.15	$30.10
Purchase #4	$173.46	4.214%	$180.7696	$180.77	$180.75	$180.80
Purchase #5	$6.94	11.813%	$7.7598	$7.76	$7.75	$7.80
Purchase #6	$86.37	10.271%	$95.2411	$95.24	$95.25	$95.20
Purchase #7	$120.86	5.625%	$127.6584	$127.66	$127.65	$127.70
7 purchase totals =	$619.32		$661.3933	$661.40	$661.35	$661.50