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	$103.89	7.211%	$111.3815	$111.38	$111.40	$111.40
Purchase #2	$143.54	9.614%	$157.3399	$157.34	$157.35	$157.30
Purchase #3	$61.34	7.551%	$65.9718	$65.97	$65.95	$66.00
Purchase #4	$96.49	9.670%	$105.8206	$105.82	$105.80	$105.80
Purchase #5	$92.87	9.666%	$101.8468	$101.85	$101.85	$101.80
Purchase #6	$142.72	5.220%	$150.17	$150.17	$150.15	$150.20
Purchase #7	$37.85	10.685%	$41.8943	$41.89	$41.90	$41.90
7 purchase totals =	$678.70		$734.4249	$734.42	$734.40	$734.40