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	$225.94	3.140%	$233.0345	$233.03	$233.05	$233.00
Purchase #2	$104.44	6.594%	$111.3268	$111.33	$111.35	$111.30
Purchase #3	$12.53	6.286%	$13.3176	$13.32	$13.30	$13.30
Purchase #4	$103.87	4.308%	$108.3447	$108.34	$108.35	$108.30
Purchase #5	$39.52	6.343%	$42.0268	$42.03	$42.05	$42.00
Purchase #6	$117.27	6.407%	$124.7835	$124.78	$124.80	$124.80
Purchase #7	$125.80	7.145%	$134.7884	$134.79	$134.80	$134.80
7 purchase totals =	$729.37		$767.6223	$767.62	$767.70	$767.50