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	$58.73	11.737%	$65.6231	$65.62	$65.60	$65.60
Purchase #2	$209.98	6.601%	$223.8408	$223.84	$223.85	$223.80
Purchase #3	$41.89	7.728%	$45.1273	$45.13	$45.15	$45.10
Purchase #4	$133.93	10.814%	$148.4132	$148.41	$148.40	$148.40
Purchase #5	$230.89	12.856%	$260.5732	$260.57	$260.55	$260.60
Purchase #6	$90.79	11.316%	$101.0638	$101.06	$101.05	$101.10
Purchase #7	$94.49	11.457%	$105.3157	$105.32	$105.30	$105.30
7 purchase totals =	$860.70		$949.9571	$949.95	$949.90	$949.90