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	$100.46	7.541%	$108.0357	$108.04	$108.05	$108.00
Purchase #2	$68.77	7.755%	$74.1031	$74.10	$74.10	$74.10
Purchase #3	$83.54	7.262%	$89.6067	$89.61	$89.60	$89.60
Purchase #4	$80.70	12.223%	$90.564	$90.56	$90.55	$90.60
Purchase #5	$156.76	13.104%	$177.3018	$177.30	$177.30	$177.30
Purchase #6	$160.31	8.199%	$173.4538	$173.45	$173.45	$173.50
Purchase #7	$66.48	8.113%	$71.8735	$71.87	$71.85	$71.90
7 purchase totals =	$717.02		$784.9386	$784.93	$784.90	$785.00