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	$82.64	8.699%	$89.8289	$89.83	$89.85	$89.80
Purchase #2	$157.58	9.161%	$172.0159	$172.02	$172.00	$172.00
Purchase #3	$18.76	9.166%	$20.4795	$20.48	$20.50	$20.50
Purchase #4	$147.73	9.390%	$161.6018	$161.60	$161.60	$161.60
Purchase #5	$147.34	12.258%	$165.4009	$165.40	$165.40	$165.40
Purchase #6	$55.61	4.304%	$58.0035	$58.00	$58.00	$58.00
Purchase #7	$77.46	10.784%	$85.8133	$85.81	$85.80	$85.80
7 purchase totals =	$687.12		$753.1438	$753.14	$753.15	$753.10