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	$121.29	8.813%	$131.9793	$131.98	$132.00	$132.00
Purchase #2	$48.63	3.188%	$50.1803	$50.18	$50.20	$50.20
Purchase #3	$200.92	11.382%	$223.7887	$223.79	$223.80	$223.80
Purchase #4	$26.44	5.157%	$27.8035	$27.80	$27.80	$27.80
Purchase #5	$37.91	7.328%	$40.688	$40.69	$40.70	$40.70
Purchase #6	$166.82	5.144%	$175.4012	$175.40	$175.40	$175.40
Purchase #7	$100.59	3.301%	$103.9105	$103.91	$103.90	$103.90
7 purchase totals =	$702.60		$753.7515	$753.75	$753.80	$753.80