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	$40.60	13.399%	$46.04	$46.04	$46.05	$46.00
Purchase #2	$81.56	9.648%	$89.4289	$89.43	$89.45	$89.40
Purchase #3	$139.55	9.451%	$152.7389	$152.74	$152.75	$152.70
Purchase #4	$187.94	3.296%	$194.1345	$194.13	$194.15	$194.10
Purchase #5	$248.78	6.268%	$264.3735	$264.37	$264.35	$264.40
Purchase #6	$31.81	3.863%	$33.0388	$33.04	$33.05	$33.00
Purchase #7	$112.63	5.568%	$118.9012	$118.90	$118.90	$118.90
7 purchase totals =	$842.87		$898.6558	$898.65	$898.70	$898.50