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	$90.89	5.493%	$95.8826	$95.88	$95.90	$95.90
Purchase #2	$45.94	10.270%	$50.658	$50.66	$50.65	$50.70
Purchase #3	$112.57	3.661%	$116.6912	$116.69	$116.70	$116.70
Purchase #4	$136.97	11.118%	$152.1983	$152.20	$152.20	$152.20
Purchase #5	$130.44	12.183%	$146.3315	$146.33	$146.35	$146.30
Purchase #6	$209.77	6.647%	$223.7134	$223.71	$223.70	$223.70
Purchase #7	$234.84	12.578%	$264.3782	$264.38	$264.40	$264.40
7 purchase totals =	$961.42		$1,049.8532	$1,049.85	$1,049.90	$1,049.90