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	$148.42	6.300%	$157.7705	$157.77	$157.75	$157.80
Purchase #2	$37.57	8.862%	$40.8995	$40.90	$40.90	$40.90
Purchase #3	$93.28	6.487%	$99.3311	$99.33	$99.35	$99.30
Purchase #4	$41.84	4.497%	$43.7215	$43.72	$43.70	$43.70
Purchase #5	$130.35	8.691%	$141.6787	$141.68	$141.70	$141.70
Purchase #6	$160.87	7.356%	$172.7036	$172.70	$172.70	$172.70
Purchase #7	$89.85	12.854%	$101.3993	$101.40	$101.40	$101.40
7 purchase totals =	$702.18		$757.5042	$757.50	$757.50	$757.50