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	$120.93	8.622%	$131.3566	$131.36	$131.35	$131.40
Purchase #2	$164.41	10.622%	$181.8736	$181.87	$181.85	$181.90
Purchase #3	$59.31	8.140%	$64.1378	$64.14	$64.15	$64.10
Purchase #4	$188.70	3.190%	$194.7195	$194.72	$194.70	$194.70
Purchase #5	$138.37	10.128%	$152.3841	$152.38	$152.40	$152.40
Purchase #6	$149.86	11.873%	$167.6529	$167.65	$167.65	$167.70
Purchase #7	$40.56	5.498%	$42.79	$42.79	$42.80	$42.80
7 purchase totals =	$862.14		$934.9145	$934.91	$934.90	$935.00