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	$92.31	6.153%	$97.9898	$97.99	$98.00	$98.00
Purchase #2	$209.31	3.835%	$217.337	$217.34	$217.35	$217.30
Purchase #3	$146.89	11.761%	$164.1657	$164.17	$164.15	$164.20
Purchase #4	$159.56	13.764%	$181.5218	$181.52	$181.50	$181.50
Purchase #5	$138.91	4.344%	$144.9443	$144.94	$144.95	$144.90
Purchase #6	$172.78	10.530%	$190.9737	$190.97	$190.95	$191.00
Purchase #7	$42.89	10.597%	$47.4351	$47.44	$47.45	$47.40
7 purchase totals =	$962.65		$1,044.3674	$1,044.37	$1,044.35	$1,044.30