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	$88.49	11.655%	$98.8035	$98.80	$98.80	$98.80
Purchase #2	$28.46	9.432%	$31.1443	$31.14	$31.15	$31.10
Purchase #3	$89.89	10.480%	$99.3105	$99.31	$99.30	$99.30
Purchase #4	$20.27	13.203%	$22.9462	$22.95	$22.95	$22.90
Purchase #5	$243.35	10.675%	$269.3276	$269.33	$269.35	$269.30
Purchase #6	$179.38	3.277%	$185.2583	$185.26	$185.25	$185.30
Purchase #7	$226.64	11.359%	$252.384	$252.38	$252.40	$252.40
7 purchase totals =	$876.48		$959.1744	$959.17	$959.20	$959.10