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	$191.60	4.347%	$199.9289	$199.93	$199.95	$199.90
Purchase #2	$179.30	3.268%	$185.1595	$185.16	$185.15	$185.20
Purchase #3	$228.72	4.781%	$239.6551	$239.66	$239.65	$239.70
Purchase #4	$50.98	11.715%	$56.9523	$56.95	$56.95	$57.00
Purchase #5	$116.33	6.172%	$123.5099	$123.51	$123.50	$123.50
Purchase #6	$36.86	6.203%	$39.1464	$39.15	$39.15	$39.10
Purchase #7	$95.45	9.536%	$104.5521	$104.55	$104.55	$104.60
7 purchase totals =	$899.24		$948.9042	$948.91	$948.90	$949.00