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	$110.72	6.590%	$118.0164	$118.02	$118.00	$118.00
Purchase #2	$31.38	5.216%	$33.0168	$33.02	$33.00	$33.00
Purchase #3	$140.73	13.451%	$159.6596	$159.66	$159.65	$159.70
Purchase #4	$164.81	4.655%	$172.4819	$172.48	$172.50	$172.50
Purchase #5	$171.27	11.190%	$190.4351	$190.44	$190.45	$190.40
Purchase #6	$176.41	11.615%	$196.9	$196.90	$196.90	$196.90
Purchase #7	$204.89	9.492%	$224.3382	$224.34	$224.35	$224.30
7 purchase totals =	$1,000.21		$1,094.8480	$1,094.86	$1,094.85	$1,094.80