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	$177.34	4.439%	$185.2121	$185.21	$185.20	$185.20
Purchase #2	$85.60	3.689%	$88.7578	$88.76	$88.75	$88.80
Purchase #3	$93.64	12.690%	$105.5229	$105.52	$105.50	$105.50
Purchase #4	$215.89	7.223%	$231.4837	$231.48	$231.50	$231.50
Purchase #5	$238.60	6.360%	$253.775	$253.78	$253.80	$253.80
Purchase #6	$223.84	12.295%	$251.3611	$251.36	$251.35	$251.40
Purchase #7	$6.55	7.255%	$7.0252	$7.03	$7.05	$7.00
7 purchase totals =	$1,041.46		$1,123.1378	$1,123.14	$1,123.15	$1,123.20