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	$202.97	4.405%	$211.9108	$211.91	$211.90	$211.90
Purchase #2	$39.52	4.852%	$41.4375	$41.44	$41.45	$41.40
Purchase #3	$44.65	12.350%	$50.1643	$50.16	$50.15	$50.20
Purchase #4	$33.37	6.682%	$35.5998	$35.60	$35.60	$35.60
Purchase #5	$126.45	9.431%	$138.3755	$138.38	$138.40	$138.40
Purchase #6	$100.30	12.451%	$112.7884	$112.79	$112.80	$112.80
Purchase #7	$69.90	9.840%	$76.7782	$76.78	$76.80	$76.80
7 purchase totals =	$617.16		$667.0545	$667.06	$667.10	$667.10