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	$107.52	8.832%	$117.0162	$117.02	$117.00	$117.00
Purchase #2	$113.70	8.360%	$123.2053	$123.21	$123.20	$123.20
Purchase #3	$104.85	13.612%	$119.1222	$119.12	$119.10	$119.10
Purchase #4	$57.95	11.267%	$64.4792	$64.48	$64.50	$64.50
Purchase #5	$119.69	8.871%	$130.3077	$130.31	$130.30	$130.30
Purchase #6	$119.57	6.869%	$127.7833	$127.78	$127.80	$127.80
Purchase #7	$191.33	13.691%	$217.525	$217.53	$217.55	$217.50
7 purchase totals =	$814.61		$899.4389	$899.45	$899.45	$899.40