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	$207.27	7.260%	$222.3178	$222.32	$222.30	$222.30
Purchase #2	$173.50	9.733%	$190.3868	$190.39	$190.40	$190.40
Purchase #3	$194.83	6.788%	$208.0551	$208.06	$208.05	$208.10
Purchase #4	$182.54	7.289%	$195.8453	$195.85	$195.85	$195.80
Purchase #5	$101.62	13.470%	$115.3082	$115.31	$115.30	$115.30
Purchase #6	$165.83	3.572%	$171.7534	$171.75	$171.75	$171.80
Purchase #7	$204.61	8.764%	$222.542	$222.54	$222.55	$222.50
7 purchase totals =	$1,230.20		$1,326.2086	$1,326.22	$1,326.20	$1,326.20