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	$152.58	10.129%	$168.0348	$168.03	$168.05	$168.00
Purchase #2	$165.96	13.150%	$187.7837	$187.78	$187.80	$187.80
Purchase #3	$222.25	13.258%	$251.7159	$251.72	$251.70	$251.70
Purchase #4	$101.96	6.763%	$108.8556	$108.86	$108.85	$108.90
Purchase #5	$75.81	13.369%	$85.945	$85.95	$85.95	$85.90
Purchase #6	$208.56	3.439%	$215.7324	$215.73	$215.75	$215.70
Purchase #7	$61.64	6.230%	$65.4802	$65.48	$65.50	$65.50
7 purchase totals =	$988.76		$1,083.5476	$1,083.55	$1,083.60	$1,083.50