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	$92.28	12.812%	$104.1029	$104.10	$104.10	$104.10
Purchase #2	$93.38	7.648%	$100.5217	$100.52	$100.50	$100.50
Purchase #3	$114.39	5.347%	$120.5064	$120.51	$120.50	$120.50
Purchase #4	$108.91	10.455%	$120.2965	$120.30	$120.30	$120.30
Purchase #5	$119.85	4.610%	$125.3751	$125.38	$125.40	$125.40
Purchase #6	$161.54	3.708%	$167.5299	$167.53	$167.55	$167.50
Purchase #7	$36.54	13.273%	$41.39	$41.39	$41.40	$41.40
7 purchase totals =	$726.89		$779.7225	$779.73	$779.75	$779.70