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	$172.73	9.129%	$188.4985	$188.50	$188.50	$188.50
Purchase #2	$98.69	5.207%	$103.8288	$103.83	$103.85	$103.80
Purchase #3	$59.52	11.625%	$66.4392	$66.44	$66.45	$66.40
Purchase #4	$108.83	4.616%	$113.8536	$113.85	$113.85	$113.90
Purchase #5	$36.82	12.513%	$41.4273	$41.43	$41.45	$41.40
Purchase #6	$225.58	11.621%	$251.7947	$251.79	$251.80	$251.80
Purchase #7	$238.34	4.193%	$248.3336	$248.33	$248.35	$248.30
7 purchase totals =	$940.51		$1,014.1757	$1,014.17	$1,014.25	$1,014.10