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	$185.39	6.216%	$196.9138	$196.91	$196.90	$196.90
Purchase #2	$223.29	9.449%	$244.3887	$244.39	$244.40	$244.40
Purchase #3	$169.73	12.264%	$190.5457	$190.55	$190.55	$190.50
Purchase #4	$200.83	4.470%	$209.8071	$209.81	$209.80	$209.80
Purchase #5	$249.52	4.327%	$260.3167	$260.32	$260.30	$260.30
Purchase #6	$44.49	5.741%	$47.0442	$47.04	$47.05	$47.00
Purchase #7	$215.38	4.608%	$225.3047	$225.30	$225.30	$225.30
7 purchase totals =	$1,288.63		$1,374.3209	$1,374.32	$1,374.30	$1,374.20