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	$125.76	11.584%	$140.328	$140.33	$140.35	$140.30
Purchase #2	$36.33	3.390%	$37.5616	$37.56	$37.55	$37.60
Purchase #3	$153.46	9.104%	$167.431	$167.43	$167.45	$167.40
Purchase #4	$37.66	10.300%	$41.539	$41.54	$41.55	$41.50
Purchase #5	$156.86	11.127%	$174.3138	$174.31	$174.30	$174.30
Purchase #6	$87.72	7.531%	$94.3262	$94.33	$94.35	$94.30
Purchase #7	$42.48	5.638%	$44.875	$44.88	$44.90	$44.90
7 purchase totals =	$640.27		$700.3746	$700.38	$700.45	$700.30