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	$239.43	3.456%	$247.7047	$247.70	$247.70	$247.70
Purchase #2	$155.37	10.633%	$171.8905	$171.89	$171.90	$171.90
Purchase #3	$96.25	6.647%	$102.6477	$102.65	$102.65	$102.60
Purchase #4	$12.78	3.130%	$13.18	$13.18	$13.20	$13.20
Purchase #5	$93.56	6.475%	$99.618	$99.62	$99.60	$99.60
Purchase #6	$162.73	11.599%	$181.6051	$181.61	$181.60	$181.60
Purchase #7	$208.52	4.492%	$217.8867	$217.89	$217.90	$217.90
7 purchase totals =	$968.64		$1,034.5327	$1,034.54	$1,034.55	$1,034.50