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	$197.28	10.416%	$217.8287	$217.83	$217.85	$217.80
Purchase #2	$179.88	4.563%	$188.0879	$188.09	$188.10	$188.10
Purchase #3	$159.65	5.171%	$167.9055	$167.91	$167.90	$167.90
Purchase #4	$167.78	10.664%	$185.6721	$185.67	$185.65	$185.70
Purchase #5	$50.44	8.851%	$54.9044	$54.90	$54.90	$54.90
Purchase #6	$206.56	9.181%	$225.5243	$225.52	$225.50	$225.50
Purchase #7	$37.70	6.866%	$40.2885	$40.29	$40.30	$40.30
7 purchase totals =	$999.29		$1,080.2114	$1,080.21	$1,080.20	$1,080.20