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	$98.95	6.394%	$105.2769	$105.28	$105.30	$105.30
Purchase #2	$30.37	7.626%	$32.686	$32.69	$32.70	$32.70
Purchase #3	$59.52	10.511%	$65.7761	$65.78	$65.80	$65.80
Purchase #4	$42.74	6.511%	$45.5228	$45.52	$45.50	$45.50
Purchase #5	$86.98	9.582%	$95.3144	$95.31	$95.30	$95.30
Purchase #6	$34.44	12.634%	$38.7911	$38.79	$38.80	$38.80
Purchase #7	$206.64	10.626%	$228.5976	$228.60	$228.60	$228.60
7 purchase totals =	$559.64		$611.9649	$611.97	$612.00	$612.00