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	$35.85	4.512%	$37.4676	$37.47	$37.45	$37.50
Purchase #2	$209.79	8.305%	$227.2131	$227.21	$227.20	$227.20
Purchase #3	$178.89	9.388%	$195.6842	$195.68	$195.70	$195.70
Purchase #4	$38.75	8.835%	$42.1736	$42.17	$42.15	$42.20
Purchase #5	$160.46	6.834%	$171.4258	$171.43	$171.45	$171.40
Purchase #6	$50.67	6.823%	$54.1272	$54.13	$54.15	$54.10
Purchase #7	$168.29	4.841%	$176.4369	$176.44	$176.45	$176.40
7 purchase totals =	$842.70		$904.5284	$904.53	$904.55	$904.50