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	$57.45	7.772%	$61.915	$61.92	$61.90	$61.90
Purchase #2	$90.65	11.699%	$101.2551	$101.26	$101.25	$101.30
Purchase #3	$237.63	12.219%	$266.666	$266.67	$266.65	$266.70
Purchase #4	$156.57	7.630%	$168.5163	$168.52	$168.50	$168.50
Purchase #5	$85.89	12.219%	$96.3849	$96.38	$96.40	$96.40
Purchase #6	$139.78	3.133%	$144.1593	$144.16	$144.15	$144.20
Purchase #7	$84.58	8.377%	$91.6653	$91.67	$91.65	$91.70
7 purchase totals =	$852.55		$930.5619	$930.58	$930.50	$930.70