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	$240.88	8.852%	$262.2027	$262.20	$262.20	$262.20
Purchase #2	$171.97	11.349%	$191.4869	$191.49	$191.50	$191.50
Purchase #3	$33.83	10.583%	$37.4102	$37.41	$37.40	$37.40
Purchase #4	$132.92	10.328%	$146.648	$146.65	$146.65	$146.60
Purchase #5	$229.98	11.690%	$256.8647	$256.86	$256.85	$256.90
Purchase #6	$54.61	12.486%	$61.4286	$61.43	$61.45	$61.40
Purchase #7	$142.63	6.811%	$152.3445	$152.34	$152.35	$152.30
7 purchase totals =	$1,006.82		$1,108.3856	$1,108.38	$1,108.40	$1,108.30