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	$147.41	3.717%	$152.8892	$152.89	$152.90	$152.90
Purchase #2	$135.38	8.473%	$146.8507	$146.85	$146.85	$146.90
Purchase #3	$180.44	5.624%	$190.5879	$190.59	$190.60	$190.60
Purchase #4	$51.69	11.545%	$57.6576	$57.66	$57.65	$57.70
Purchase #5	$89.94	3.722%	$93.2876	$93.29	$93.30	$93.30
Purchase #6	$234.97	13.156%	$265.8827	$265.88	$265.90	$265.90
Purchase #7	$185.38	6.244%	$196.9551	$196.96	$196.95	$197.00
7 purchase totals =	$1,025.21		$1,104.1108	$1,104.12	$1,104.15	$1,104.30