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	$99.94	8.309%	$108.244	$108.24	$108.25	$108.20
Purchase #2	$140.29	7.316%	$150.5536	$150.55	$150.55	$150.60
Purchase #3	$181.79	3.168%	$187.5491	$187.55	$187.55	$187.50
Purchase #4	$74.47	5.460%	$78.5361	$78.54	$78.55	$78.50
Purchase #5	$246.63	5.406%	$259.9628	$259.96	$259.95	$260.00
Purchase #6	$174.52	5.141%	$183.4921	$183.49	$183.50	$183.50
Purchase #7	$86.47	11.648%	$96.542	$96.54	$96.55	$96.50
7 purchase totals =	$1,004.11		$1,064.8797	$1,064.87	$1,064.90	$1,064.80