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	$56.58	10.176%	$62.3376	$62.34	$62.35	$62.30
Purchase #2	$119.69	7.645%	$128.8403	$128.84	$128.85	$128.80
Purchase #3	$250.44	7.506%	$269.238	$269.24	$269.25	$269.20
Purchase #4	$74.65	11.587%	$83.2997	$83.30	$83.30	$83.30
Purchase #5	$199.51	5.241%	$209.9663	$209.97	$209.95	$210.00
Purchase #6	$112.53	11.873%	$125.8907	$125.89	$125.90	$125.90
Purchase #7	$79.83	12.168%	$89.5437	$89.54	$89.55	$89.50
7 purchase totals =	$893.23		$969.1163	$969.12	$969.15	$969.00