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	$184.54	6.580%	$196.6827	$196.68	$196.70	$196.70
Purchase #2	$115.89	11.685%	$129.4317	$129.43	$129.45	$129.40
Purchase #3	$136.32	12.616%	$153.5181	$153.52	$153.50	$153.50
Purchase #4	$73.85	8.766%	$80.3237	$80.32	$80.30	$80.30
Purchase #5	$54.74	5.188%	$57.5799	$57.58	$57.60	$57.60
Purchase #6	$33.46	13.347%	$37.9259	$37.93	$37.95	$37.90
Purchase #7	$95.58	11.465%	$106.5382	$106.54	$106.55	$106.50
7 purchase totals =	$694.38		$762.0002	$762.00	$762.05	$761.90