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	$59.79	8.545%	$64.8991	$64.90	$64.90	$64.90
Purchase #2	$169.44	7.197%	$181.6346	$181.63	$181.65	$181.60
Purchase #3	$110.82	11.764%	$123.8569	$123.86	$123.85	$123.90
Purchase #4	$182.79	7.455%	$196.417	$196.42	$196.40	$196.40
Purchase #5	$60.55	6.653%	$64.5784	$64.58	$64.60	$64.60
Purchase #6	$225.78	4.801%	$236.6197	$236.62	$236.60	$236.60
Purchase #7	$89.73	5.668%	$94.8159	$94.82	$94.80	$94.80
7 purchase totals =	$898.90		$962.8216	$962.83	$962.80	$962.80