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	$110.88	11.652%	$123.7997	$123.80	$123.80	$123.80
Purchase #2	$6.73	8.794%	$7.3218	$7.32	$7.30	$7.30
Purchase #3	$122.93	4.203%	$128.0967	$128.10	$128.10	$128.10
Purchase #4	$140.28	6.118%	$148.8623	$148.86	$148.85	$148.90
Purchase #5	$155.83	10.146%	$171.6405	$171.64	$171.65	$171.60
Purchase #6	$9.86	13.234%	$11.1649	$11.16	$11.15	$11.20
Purchase #7	$98.80	13.179%	$111.8209	$111.82	$111.80	$111.80
7 purchase totals =	$645.31		$702.7068	$702.70	$702.65	$702.70