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	$180.50	5.437%	$190.3138	$190.31	$190.30	$190.30
Purchase #2	$24.30	11.723%	$27.1487	$27.15	$27.15	$27.10
Purchase #3	$26.47	3.714%	$27.4531	$27.45	$27.45	$27.50
Purchase #4	$137.97	6.184%	$146.5021	$146.50	$146.50	$146.50
Purchase #5	$164.33	11.539%	$183.292	$183.29	$183.30	$183.30
Purchase #6	$75.47	6.780%	$80.5869	$80.59	$80.60	$80.60
Purchase #7	$223.72	13.246%	$253.354	$253.35	$253.35	$253.40
7 purchase totals =	$832.76		$908.6506	$908.64	$908.65	$908.70