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	$176.59	4.405%	$184.3688	$184.37	$184.35	$184.40
Purchase #2	$55.63	6.659%	$59.3344	$59.33	$59.35	$59.30
Purchase #3	$114.76	12.374%	$128.9604	$128.96	$128.95	$129.00
Purchase #4	$132.41	8.545%	$143.7244	$143.72	$143.70	$143.70
Purchase #5	$141.55	5.697%	$149.6141	$149.61	$149.60	$149.60
Purchase #6	$42.71	10.251%	$47.0882	$47.09	$47.10	$47.10
Purchase #7	$40.26	6.398%	$42.8358	$42.84	$42.85	$42.80
7 purchase totals =	$703.91		$755.9261	$755.92	$755.90	$755.90