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	$94.33	11.326%	$105.0138	$105.01	$105.00	$105.00
Purchase #2	$143.33	8.743%	$155.8613	$155.86	$155.85	$155.90
Purchase #3	$244.62	8.564%	$265.5693	$265.57	$265.55	$265.60
Purchase #4	$149.70	5.274%	$157.5952	$157.60	$157.60	$157.60
Purchase #5	$125.77	7.193%	$134.8166	$134.82	$134.80	$134.80
Purchase #6	$128.42	3.865%	$133.3834	$133.38	$133.40	$133.40
Purchase #7	$187.40	4.603%	$196.026	$196.03	$196.05	$196.00
7 purchase totals =	$1,073.57		$1,148.2656	$1,148.27	$1,148.25	$1,148.30