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	$165.76	5.275%	$174.5038	$174.50	$174.50	$174.50
Purchase #2	$232.27	9.859%	$255.1695	$255.17	$255.15	$255.20
Purchase #3	$32.89	12.761%	$37.0871	$37.09	$37.10	$37.10
Purchase #4	$112.86	6.163%	$119.8156	$119.82	$119.80	$119.80
Purchase #5	$59.64	11.562%	$66.5356	$66.54	$66.55	$66.50
Purchase #6	$220.34	3.714%	$228.5234	$228.52	$228.50	$228.50
Purchase #7	$30.73	6.356%	$32.6832	$32.68	$32.70	$32.70
7 purchase totals =	$854.49		$914.3182	$914.32	$914.30	$914.30