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	$124.78	6.315%	$132.6599	$132.66	$132.65	$132.70
Purchase #2	$250.50	3.173%	$258.4484	$258.45	$258.45	$258.40
Purchase #3	$136.83	5.727%	$144.6663	$144.67	$144.65	$144.70
Purchase #4	$195.30	8.602%	$212.0997	$212.10	$212.10	$212.10
Purchase #5	$106.72	7.444%	$114.6642	$114.66	$114.65	$114.70
Purchase #6	$112.76	12.713%	$127.0952	$127.10	$127.10	$127.10
Purchase #7	$169.50	13.221%	$191.9096	$191.91	$191.90	$191.90
7 purchase totals =	$1,096.39		$1,181.5433	$1,181.55	$1,181.50	$1,181.60