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	$65.47	9.136%	$71.4513	$71.45	$71.45	$71.50
Purchase #2	$195.78	10.608%	$216.5483	$216.55	$216.55	$216.50
Purchase #3	$72.73	12.126%	$81.5492	$81.55	$81.55	$81.50
Purchase #4	$51.78	4.530%	$54.1256	$54.13	$54.15	$54.10
Purchase #5	$180.47	6.387%	$191.9966	$192.00	$192.00	$192.00
Purchase #6	$79.64	13.292%	$90.2257	$90.23	$90.25	$90.20
Purchase #7	$33.66	13.505%	$38.2058	$38.21	$38.20	$38.20
7 purchase totals =	$679.53		$744.1025	$744.12	$744.15	$744.00