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	$117.62	11.831%	$131.5356	$131.54	$131.55	$131.50
Purchase #2	$169.40	7.727%	$182.4895	$182.49	$182.50	$182.50
Purchase #3	$175.97	11.750%	$196.6465	$196.65	$196.65	$196.60
Purchase #4	$119.53	3.343%	$123.5259	$123.53	$123.55	$123.50
Purchase #5	$89.38	4.830%	$93.6971	$93.70	$93.70	$93.70
Purchase #6	$86.64	8.569%	$94.0642	$94.06	$94.05	$94.10
Purchase #7	$136.91	6.772%	$146.1815	$146.18	$146.20	$146.20
7 purchase totals =	$895.45		$968.1403	$968.15	$968.20	$968.10