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	$167.82	13.520%	$190.5093	$190.51	$190.50	$190.50
Purchase #2	$57.63	3.369%	$59.5716	$59.57	$59.55	$59.60
Purchase #3	$71.72	3.236%	$74.0409	$74.04	$74.05	$74.00
Purchase #4	$186.41	3.801%	$193.4954	$193.50	$193.50	$193.50
Purchase #5	$242.89	12.346%	$272.8772	$272.88	$272.90	$272.90
Purchase #6	$45.48	13.636%	$51.6817	$51.68	$51.70	$51.70
Purchase #7	$162.55	4.749%	$170.2695	$170.27	$170.25	$170.30
7 purchase totals =	$934.50		$1,012.4456	$1,012.45	$1,012.45	$1,012.50