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	$132.41	13.499%	$150.284	$150.28	$150.30	$150.30
Purchase #2	$223.39	12.665%	$251.6823	$251.68	$251.70	$251.70
Purchase #3	$81.76	10.550%	$90.3857	$90.39	$90.40	$90.40
Purchase #4	$56.74	5.674%	$59.9594	$59.96	$59.95	$60.00
Purchase #5	$21.32	12.580%	$24.0021	$24.00	$24.00	$24.00
Purchase #6	$200.59	4.269%	$209.1532	$209.15	$209.15	$209.20
Purchase #7	$119.96	7.158%	$128.5467	$128.55	$128.55	$128.50
7 purchase totals =	$836.17		$914.0134	$914.01	$914.05	$914.10