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	$226.59	10.605%	$250.6199	$250.62	$250.60	$250.60
Purchase #2	$157.43	13.305%	$178.3761	$178.38	$178.40	$178.40
Purchase #3	$236.95	11.444%	$264.0666	$264.07	$264.05	$264.10
Purchase #4	$136.47	5.395%	$143.8326	$143.83	$143.85	$143.80
Purchase #5	$91.26	6.293%	$97.003	$97.00	$97.00	$97.00
Purchase #6	$45.26	5.865%	$47.9145	$47.91	$47.90	$47.90
Purchase #7	$34.41	8.183%	$37.2258	$37.23	$37.25	$37.20
7 purchase totals =	$928.37		$1,019.0385	$1,019.04	$1,019.05	$1,019.00