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	$116.69	11.866%	$130.5364	$130.54	$130.55	$130.50
Purchase #2	$169.88	13.694%	$193.1434	$193.14	$193.15	$193.10
Purchase #3	$224.39	9.416%	$245.5186	$245.52	$245.50	$245.50
Purchase #4	$8.89	13.830%	$10.1195	$10.12	$10.10	$10.10
Purchase #5	$119.61	9.565%	$131.0507	$131.05	$131.05	$131.10
Purchase #6	$146.73	6.666%	$156.511	$156.51	$156.50	$156.50
Purchase #7	$34.99	12.824%	$39.4771	$39.48	$39.50	$39.50
7 purchase totals =	$821.18		$906.3567	$906.36	$906.35	$906.30