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	$87.58	4.826%	$91.8066	$91.81	$91.80	$91.80
Purchase #2	$191.40	13.163%	$216.594	$216.59	$216.60	$216.60
Purchase #3	$5.25	4.323%	$5.477	$5.48	$5.50	$5.50
Purchase #4	$6.28	10.357%	$6.9304	$6.93	$6.95	$6.90
Purchase #5	$139.83	3.596%	$144.8583	$144.86	$144.85	$144.90
Purchase #6	$78.69	4.409%	$82.1594	$82.16	$82.15	$82.20
Purchase #7	$146.50	12.867%	$165.3502	$165.35	$165.35	$165.40
7 purchase totals =	$655.53		$713.1759	$713.18	$713.20	$713.30