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	$82.85	3.438%	$85.6984	$85.70	$85.70	$85.70
Purchase #2	$173.65	5.678%	$183.5098	$183.51	$183.50	$183.50
Purchase #3	$164.70	7.190%	$176.5419	$176.54	$176.55	$176.50
Purchase #4	$53.70	5.692%	$56.7566	$56.76	$56.75	$56.80
Purchase #5	$148.46	11.355%	$165.3176	$165.32	$165.30	$165.30
Purchase #6	$57.65	3.167%	$59.4758	$59.48	$59.50	$59.50
Purchase #7	$14.77	10.364%	$16.3008	$16.30	$16.30	$16.30
7 purchase totals =	$695.78		$743.6009	$743.61	$743.60	$743.60