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	$131.75	7.818%	$142.0502	$142.05	$142.05	$142.10
Purchase #2	$192.96	11.588%	$215.3202	$215.32	$215.30	$215.30
Purchase #3	$22.30	10.594%	$24.6625	$24.66	$24.65	$24.70
Purchase #4	$63.86	8.185%	$69.0869	$69.09	$69.10	$69.10
Purchase #5	$11.91	8.219%	$12.8889	$12.89	$12.90	$12.90
Purchase #6	$48.42	12.522%	$54.4832	$54.48	$54.50	$54.50
Purchase #7	$92.88	6.841%	$99.2339	$99.23	$99.25	$99.20
7 purchase totals =	$564.08		$617.7258	$617.72	$617.75	$617.80