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	$80.85	13.248%	$91.561	$91.56	$91.55	$91.60
Purchase #2	$160.58	12.665%	$180.9175	$180.92	$180.90	$180.90
Purchase #3	$37.36	11.643%	$41.7098	$41.71	$41.70	$41.70
Purchase #4	$114.84	4.403%	$119.8964	$119.90	$119.90	$119.90
Purchase #5	$226.83	7.386%	$243.5837	$243.58	$243.60	$243.60
Purchase #6	$50.91	13.701%	$57.8852	$57.89	$57.90	$57.90
Purchase #7	$177.89	9.239%	$194.3253	$194.33	$194.35	$194.30
7 purchase totals =	$849.26		$929.8789	$929.89	$929.90	$929.90