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	$29.86	11.184%	$33.1995	$33.20	$33.20	$33.20
Purchase #2	$40.27	9.151%	$43.9551	$43.96	$43.95	$44.00
Purchase #3	$218.82	11.453%	$243.8815	$243.88	$243.90	$243.90
Purchase #4	$212.36	10.370%	$234.3817	$234.38	$234.40	$234.40
Purchase #5	$243.58	8.665%	$264.6862	$264.69	$264.70	$264.70
Purchase #6	$136.74	11.834%	$152.9218	$152.92	$152.90	$152.90
Purchase #7	$111.94	6.838%	$119.5945	$119.59	$119.60	$119.60
7 purchase totals =	$993.57		$1,092.6203	$1,092.62	$1,092.65	$1,092.70