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	$81.42	4.272%	$84.8983	$84.90	$84.90	$84.90
Purchase #2	$61.64	13.214%	$69.7851	$69.79	$69.80	$69.80
Purchase #3	$162.84	5.516%	$171.8223	$171.82	$171.80	$171.80
Purchase #4	$52.77	12.302%	$59.2618	$59.26	$59.25	$59.30
Purchase #5	$241.80	7.534%	$260.0172	$260.02	$260.00	$260.00
Purchase #6	$162.51	13.417%	$184.314	$184.31	$184.30	$184.30
Purchase #7	$229.85	7.661%	$247.4588	$247.46	$247.45	$247.50
7 purchase totals =	$992.83		$1,077.5575	$1,077.56	$1,077.50	$1,077.60