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	$41.99	3.629%	$43.5138	$43.51	$43.50	$43.50
Purchase #2	$81.33	4.873%	$85.2932	$85.29	$85.30	$85.30
Purchase #3	$32.72	13.722%	$37.2098	$37.21	$37.20	$37.20
Purchase #4	$127.83	11.549%	$142.5931	$142.59	$142.60	$142.60
Purchase #5	$85.80	12.552%	$96.5696	$96.57	$96.55	$96.60
Purchase #6	$36.53	4.300%	$38.1008	$38.10	$38.10	$38.10
Purchase #7	$226.99	11.853%	$253.8951	$253.90	$253.90	$253.90
7 purchase totals =	$633.19		$697.1754	$697.17	$697.15	$697.20