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	$147.59	12.806%	$166.4904	$166.49	$166.50	$166.50
Purchase #2	$117.61	4.833%	$123.2941	$123.29	$123.30	$123.30
Purchase #3	$185.86	12.792%	$209.6352	$209.64	$209.65	$209.60
Purchase #4	$236.55	11.551%	$263.8739	$263.87	$263.85	$263.90
Purchase #5	$237.95	13.244%	$269.4641	$269.46	$269.45	$269.50
Purchase #6	$215.66	8.494%	$233.9782	$233.98	$234.00	$234.00
Purchase #7	$217.94	6.477%	$232.056	$232.06	$232.05	$232.10
7 purchase totals =	$1,359.16		$1,498.7919	$1,498.79	$1,498.80	$1,498.90