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	$82.88	9.595%	$90.8323	$90.83	$90.85	$90.80
Purchase #2	$151.52	11.329%	$168.6857	$168.69	$168.70	$168.70
Purchase #3	$222.42	7.299%	$238.6544	$238.65	$238.65	$238.70
Purchase #4	$191.57	13.432%	$217.3017	$217.30	$217.30	$217.30
Purchase #5	$191.73	6.865%	$204.8923	$204.89	$204.90	$204.90
Purchase #6	$162.58	5.182%	$171.0049	$171.00	$171.00	$171.00
Purchase #7	$107.47	3.341%	$111.0606	$111.06	$111.05	$111.10
7 purchase totals =	$1,110.17		$1,202.4319	$1,202.42	$1,202.45	$1,202.50