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	$82.52	5.547%	$87.0974	$87.10	$87.10	$87.10
Purchase #2	$68.89	13.389%	$78.1137	$78.11	$78.10	$78.10
Purchase #3	$37.90	12.717%	$42.7197	$42.72	$42.70	$42.70
Purchase #4	$92.65	6.548%	$98.7167	$98.72	$98.70	$98.70
Purchase #5	$109.34	3.130%	$112.7623	$112.76	$112.75	$112.80
Purchase #6	$153.76	13.486%	$174.4961	$174.50	$174.50	$174.50
Purchase #7	$77.55	4.236%	$80.835	$80.84	$80.85	$80.80
7 purchase totals =	$622.61		$674.7409	$674.75	$674.70	$674.70