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	$41.69	6.424%	$44.3682	$44.37	$44.35	$44.40
Purchase #2	$160.91	6.614%	$171.5526	$171.55	$171.55	$171.60
Purchase #3	$72.39	10.593%	$80.0583	$80.06	$80.05	$80.10
Purchase #4	$86.92	4.671%	$90.98	$90.98	$91.00	$91.00
Purchase #5	$133.85	5.230%	$140.8504	$140.85	$140.85	$140.90
Purchase #6	$148.52	10.502%	$164.1176	$164.12	$164.10	$164.10
Purchase #7	$32.91	6.637%	$35.0942	$35.09	$35.10	$35.10
7 purchase totals =	$677.19		$727.0213	$727.02	$727.00	$727.20