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	$112.25	6.487%	$119.5317	$119.53	$119.55	$119.50
Purchase #2	$54.64	9.236%	$59.6866	$59.69	$59.70	$59.70
Purchase #3	$117.89	10.250%	$129.9737	$129.97	$129.95	$130.00
Purchase #4	$103.30	13.137%	$116.8705	$116.87	$116.85	$116.90
Purchase #5	$57.84	5.459%	$60.9975	$61.00	$61.00	$61.00
Purchase #6	$109.77	12.240%	$123.2058	$123.21	$123.20	$123.20
Purchase #7	$74.32	8.571%	$80.69	$80.69	$80.70	$80.70
7 purchase totals =	$630.01		$690.9558	$690.96	$690.95	$691.00