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	$212.82	13.188%	$240.8867	$240.89	$240.90	$240.90
Purchase #2	$52.47	6.847%	$56.0626	$56.06	$56.05	$56.10
Purchase #3	$215.37	6.577%	$229.5349	$229.53	$229.55	$229.50
Purchase #4	$173.43	13.350%	$196.5829	$196.58	$196.60	$196.60
Purchase #5	$244.68	6.459%	$260.4839	$260.48	$260.50	$260.50
Purchase #6	$11.86	10.848%	$13.1466	$13.15	$13.15	$13.10
Purchase #7	$24.39	11.809%	$27.2702	$27.27	$27.25	$27.30
7 purchase totals =	$935.02		$1,023.9678	$1,023.96	$1,024.00	$1,024.00