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	$85.72	7.664%	$92.2896	$92.29	$92.30	$92.30
Purchase #2	$65.84	6.801%	$70.3178	$70.32	$70.30	$70.30
Purchase #3	$147.54	3.145%	$152.1801	$152.18	$152.20	$152.20
Purchase #4	$112.31	13.596%	$127.5797	$127.58	$127.60	$127.60
Purchase #5	$180.79	7.701%	$194.7126	$194.71	$194.70	$194.70
Purchase #6	$67.45	5.572%	$71.2083	$71.21	$71.20	$71.20
Purchase #7	$152.82	3.697%	$158.4698	$158.47	$158.45	$158.50
7 purchase totals =	$812.47		$866.7579	$866.76	$866.75	$866.80