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	$84.86	7.775%	$91.4579	$91.46	$91.45	$91.50
Purchase #2	$93.67	13.689%	$106.4925	$106.49	$106.50	$106.50
Purchase #3	$242.48	10.480%	$267.8919	$267.89	$267.90	$267.90
Purchase #4	$141.53	3.565%	$146.5755	$146.58	$146.60	$146.60
Purchase #5	$131.31	6.102%	$139.3225	$139.32	$139.30	$139.30
Purchase #6	$174.38	5.415%	$183.8227	$183.82	$183.80	$183.80
Purchase #7	$31.38	4.802%	$32.8869	$32.89	$32.90	$32.90
7 purchase totals =	$899.61		$968.4499	$968.45	$968.45	$968.50