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	$122.48	3.130%	$126.3136	$126.31	$126.30	$126.30
Purchase #2	$41.36	4.449%	$43.2001	$43.20	$43.20	$43.20
Purchase #3	$173.75	3.873%	$180.4793	$180.48	$180.50	$180.50
Purchase #4	$131.39	11.372%	$146.3317	$146.33	$146.35	$146.30
Purchase #5	$180.42	3.604%	$186.9223	$186.92	$186.90	$186.90
Purchase #6	$57.34	6.688%	$61.1749	$61.17	$61.15	$61.20
Purchase #7	$227.72	8.532%	$247.1491	$247.15	$247.15	$247.10
7 purchase totals =	$934.46		$991.5710	$991.56	$991.55	$991.50