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	$112.87	4.850%	$118.3442	$118.34	$118.35	$118.30
Purchase #2	$246.69	5.690%	$260.7267	$260.73	$260.75	$260.70
Purchase #3	$34.33	3.262%	$35.4498	$35.45	$35.45	$35.40
Purchase #4	$81.51	11.816%	$91.1412	$91.14	$91.15	$91.10
Purchase #5	$155.67	12.580%	$175.2533	$175.25	$175.25	$175.30
Purchase #6	$153.70	5.672%	$162.4179	$162.42	$162.40	$162.40
Purchase #7	$77.28	10.547%	$85.4307	$85.43	$85.45	$85.40
7 purchase totals =	$862.05		$928.7638	$928.76	$928.80	$928.60