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	$149.32	11.223%	$166.0782	$166.08	$166.10	$166.10
Purchase #2	$73.97	12.538%	$83.2444	$83.24	$83.25	$83.20
Purchase #3	$109.71	5.738%	$116.0052	$116.01	$116.00	$116.00
Purchase #4	$195.72	13.680%	$222.4945	$222.49	$222.50	$222.50
Purchase #5	$94.75	4.626%	$99.1331	$99.13	$99.15	$99.10
Purchase #6	$228.76	8.218%	$247.5595	$247.56	$247.55	$247.60
Purchase #7	$42.33	4.331%	$44.1633	$44.16	$44.15	$44.20
7 purchase totals =	$894.56		$978.6782	$978.67	$978.70	$978.70