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	$197.28	8.231%	$213.5181	$213.52	$213.50	$213.50
Purchase #2	$52.28	4.479%	$54.6216	$54.62	$54.60	$54.60
Purchase #3	$51.99	4.422%	$54.289	$54.29	$54.30	$54.30
Purchase #4	$57.49	3.454%	$59.4757	$59.48	$59.50	$59.50
Purchase #5	$158.40	4.157%	$164.9847	$164.98	$165.00	$165.00
Purchase #6	$141.54	8.302%	$153.2907	$153.29	$153.30	$153.30
Purchase #7	$240.75	13.653%	$273.6196	$273.62	$273.60	$273.60
7 purchase totals =	$899.73		$973.7994	$973.80	$973.80	$973.80