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	$62.84	4.496%	$65.6653	$65.67	$65.65	$65.70
Purchase #2	$132.34	13.475%	$150.1728	$150.17	$150.15	$150.20
Purchase #3	$6.56	5.781%	$6.9392	$6.94	$6.95	$6.90
Purchase #4	$62.82	4.732%	$65.7926	$65.79	$65.80	$65.80
Purchase #5	$65.78	3.355%	$67.9869	$67.99	$68.00	$68.00
Purchase #6	$146.47	12.259%	$164.4258	$164.43	$164.45	$164.40
Purchase #7	$137.88	3.549%	$142.7734	$142.77	$142.75	$142.80
7 purchase totals =	$614.69		$663.7560	$663.76	$663.75	$663.80