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	$18.46	4.154%	$19.2268	$19.23	$19.25	$19.20
Purchase #2	$65.78	9.277%	$71.8824	$71.88	$71.90	$71.90
Purchase #3	$220.59	5.502%	$232.7269	$232.73	$232.75	$232.70
Purchase #4	$56.57	8.148%	$61.1793	$61.18	$61.20	$61.20
Purchase #5	$59.92	11.191%	$66.6256	$66.63	$66.65	$66.60
Purchase #6	$167.94	7.762%	$180.9755	$180.98	$181.00	$181.00
Purchase #7	$155.26	10.721%	$171.9054	$171.91	$171.90	$171.90
7 purchase totals =	$744.52		$804.5219	$804.54	$804.65	$804.50