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	$200.56	11.141%	$222.9044	$222.90	$222.90	$222.90
Purchase #2	$188.45	11.170%	$209.4999	$209.50	$209.50	$209.50
Purchase #3	$93.34	12.444%	$104.9552	$104.96	$104.95	$105.00
Purchase #4	$90.39	10.394%	$99.7851	$99.79	$99.80	$99.80
Purchase #5	$135.99	7.779%	$146.5687	$146.57	$146.55	$146.60
Purchase #6	$190.56	5.317%	$200.6921	$200.69	$200.70	$200.70
Purchase #7	$56.66	6.421%	$60.2981	$60.30	$60.30	$60.30
7 purchase totals =	$955.95		$1,044.7035	$1,044.71	$1,044.70	$1,044.80