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	$127.96	13.244%	$144.907	$144.91	$144.90	$144.90
Purchase #2	$9.77	7.227%	$10.4761	$10.48	$10.50	$10.50
Purchase #3	$27.32	9.349%	$29.8741	$29.87	$29.85	$29.90
Purchase #4	$37.91	12.839%	$42.7773	$42.78	$42.80	$42.80
Purchase #5	$6.77	4.830%	$7.097	$7.10	$7.10	$7.10
Purchase #6	$249.91	10.391%	$275.8781	$275.88	$275.90	$275.90
Purchase #7	$53.51	12.113%	$59.9917	$59.99	$60.00	$60.00
7 purchase totals =	$513.15		$571.0013	$571.01	$571.05	$571.10