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	$179.41	10.444%	$198.1476	$198.15	$198.15	$198.10
Purchase #2	$239.53	13.808%	$272.6043	$272.60	$272.60	$272.60
Purchase #3	$174.54	9.467%	$191.0637	$191.06	$191.05	$191.10
Purchase #4	$82.81	5.756%	$87.5765	$87.58	$87.60	$87.60
Purchase #5	$6.38	7.756%	$6.8748	$6.87	$6.85	$6.90
Purchase #6	$82.42	10.581%	$91.1409	$91.14	$91.15	$91.10
Purchase #7	$206.72	10.810%	$229.0664	$229.07	$229.05	$229.10
7 purchase totals =	$971.81		$1,076.4742	$1,076.47	$1,076.45	$1,076.50