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	$213.86	6.524%	$227.8122	$227.81	$227.80	$227.80
Purchase #2	$41.57	9.545%	$45.5379	$45.54	$45.55	$45.50
Purchase #3	$144.81	9.304%	$158.2831	$158.28	$158.30	$158.30
Purchase #4	$88.99	13.395%	$100.9102	$100.91	$100.90	$100.90
Purchase #5	$22.80	7.781%	$24.5741	$24.57	$24.55	$24.60
Purchase #6	$232.62	8.104%	$251.4715	$251.47	$251.45	$251.50
Purchase #7	$79.60	11.749%	$88.9522	$88.95	$88.95	$89.00
7 purchase totals =	$824.25		$897.5412	$897.53	$897.50	$897.60