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	$88.37	13.222%	$100.0543	$100.05	$100.05	$100.10
Purchase #2	$175.42	3.241%	$181.1054	$181.11	$181.10	$181.10
Purchase #3	$167.39	7.467%	$179.889	$179.89	$179.90	$179.90
Purchase #4	$102.76	13.683%	$116.8207	$116.82	$116.80	$116.80
Purchase #5	$45.51	7.810%	$49.0643	$49.06	$49.05	$49.10
Purchase #6	$238.61	12.862%	$269.3	$269.30	$269.30	$269.30
Purchase #7	$138.48	8.575%	$150.3547	$150.35	$150.35	$150.40
7 purchase totals =	$956.54		$1,046.5884	$1,046.58	$1,046.55	$1,046.70