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	$119.88	11.232%	$133.3449	$133.34	$133.35	$133.30
Purchase #2	$167.63	8.508%	$181.892	$181.89	$181.90	$181.90
Purchase #3	$64.57	6.733%	$68.9175	$68.92	$68.90	$68.90
Purchase #4	$152.25	10.497%	$168.2317	$168.23	$168.25	$168.20
Purchase #5	$42.58	7.730%	$45.8714	$45.87	$45.85	$45.90
Purchase #6	$222.55	6.213%	$236.377	$236.38	$236.40	$236.40
Purchase #7	$84.60	5.482%	$89.2378	$89.24	$89.25	$89.20
7 purchase totals =	$854.06		$923.8723	$923.87	$923.90	$923.80