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	$143.46	6.700%	$153.0718	$153.07	$153.05	$153.10
Purchase #2	$133.72	3.142%	$137.9215	$137.92	$137.90	$137.90
Purchase #3	$111.59	12.477%	$125.5131	$125.51	$125.50	$125.50
Purchase #4	$208.29	10.320%	$229.7855	$229.79	$229.80	$229.80
Purchase #5	$169.81	3.308%	$175.4273	$175.43	$175.45	$175.40
Purchase #6	$86.25	10.589%	$95.383	$95.38	$95.40	$95.40
Purchase #7	$250.47	4.612%	$262.0217	$262.02	$262.00	$262.00
7 purchase totals =	$1,103.59		$1,179.1239	$1,179.12	$1,179.10	$1,179.10