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	$42.61	9.428%	$46.6273	$46.63	$46.65	$46.60
Purchase #2	$110.43	3.729%	$114.5479	$114.55	$114.55	$114.50
Purchase #3	$208.39	13.675%	$236.8873	$236.89	$236.90	$236.90
Purchase #4	$204.94	7.287%	$219.874	$219.87	$219.85	$219.90
Purchase #5	$6.94	9.445%	$7.5955	$7.60	$7.60	$7.60
Purchase #6	$46.53	8.562%	$50.5139	$50.51	$50.50	$50.50
Purchase #7	$162.98	13.550%	$185.0638	$185.06	$185.05	$185.10
7 purchase totals =	$782.82		$861.1097	$861.11	$861.10	$861.10