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	$84.89	10.576%	$93.868	$93.87	$93.85	$93.90
Purchase #2	$209.62	8.177%	$226.7606	$226.76	$226.75	$226.80
Purchase #3	$212.78	4.614%	$222.5977	$222.60	$222.60	$222.60
Purchase #4	$172.90	12.394%	$194.3292	$194.33	$194.35	$194.30
Purchase #5	$82.45	4.173%	$85.8906	$85.89	$85.90	$85.90
Purchase #6	$79.58	4.151%	$82.8834	$82.88	$82.90	$82.90
Purchase #7	$165.29	10.168%	$182.0967	$182.10	$182.10	$182.10
7 purchase totals =	$1,007.51		$1,088.4262	$1,088.43	$1,088.45	$1,088.50