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	$187.47	4.635%	$196.1592	$196.16	$196.15	$196.20
Purchase #2	$94.41	12.125%	$105.8572	$105.86	$105.85	$105.90
Purchase #3	$72.69	6.257%	$77.2382	$77.24	$77.25	$77.20
Purchase #4	$117.41	12.714%	$132.3375	$132.34	$132.35	$132.30
Purchase #5	$90.29	9.275%	$98.6644	$98.66	$98.65	$98.70
Purchase #6	$90.48	3.411%	$93.5663	$93.57	$93.55	$93.60
Purchase #7	$150.94	13.620%	$171.498	$171.50	$171.50	$171.50
7 purchase totals =	$803.69		$875.3208	$875.33	$875.30	$875.40