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	$223.74	4.483%	$233.7703	$233.77	$233.75	$233.80
Purchase #2	$19.67	10.443%	$21.7241	$21.72	$21.70	$21.70
Purchase #3	$126.44	10.360%	$139.5392	$139.54	$139.55	$139.50
Purchase #4	$245.38	10.223%	$270.4652	$270.47	$270.45	$270.50
Purchase #5	$127.49	11.250%	$141.8326	$141.83	$141.85	$141.80
Purchase #6	$72.38	8.803%	$78.7516	$78.75	$78.75	$78.80
Purchase #7	$218.63	4.137%	$227.6747	$227.67	$227.65	$227.70
7 purchase totals =	$1,033.73		$1,113.7577	$1,113.75	$1,113.70	$1,113.80