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	$160.76	7.253%	$172.4199	$172.42	$172.40	$172.40
Purchase #2	$106.85	5.367%	$112.5846	$112.58	$112.60	$112.60
Purchase #3	$204.48	3.381%	$211.3935	$211.39	$211.40	$211.40
Purchase #4	$123.76	6.428%	$131.7153	$131.72	$131.70	$131.70
Purchase #5	$178.51	7.687%	$192.2321	$192.23	$192.25	$192.20
Purchase #6	$83.99	6.507%	$89.4552	$89.46	$89.45	$89.50
Purchase #7	$44.72	8.574%	$48.5543	$48.55	$48.55	$48.60
7 purchase totals =	$903.07		$958.3549	$958.35	$958.35	$958.40