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	$118.85	8.456%	$128.9	$128.90	$128.90	$128.90
Purchase #2	$155.65	10.774%	$172.4197	$172.42	$172.40	$172.40
Purchase #3	$95.52	10.225%	$105.2869	$105.29	$105.30	$105.30
Purchase #4	$96.52	5.185%	$101.5246	$101.52	$101.50	$101.50
Purchase #5	$155.67	10.857%	$172.5711	$172.57	$172.55	$172.60
Purchase #6	$121.40	4.819%	$127.2503	$127.25	$127.25	$127.30
Purchase #7	$91.84	5.147%	$96.567	$96.57	$96.55	$96.60
7 purchase totals =	$835.45		$904.5196	$904.52	$904.45	$904.60