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	$175.77	9.165%	$191.8793	$191.88	$191.90	$191.90
Purchase #2	$122.96	10.665%	$136.0737	$136.07	$136.05	$136.10
Purchase #3	$206.54	7.170%	$221.3489	$221.35	$221.35	$221.30
Purchase #4	$103.30	3.201%	$106.6066	$106.61	$106.60	$106.60
Purchase #5	$13.69	12.848%	$15.4489	$15.45	$15.45	$15.40
Purchase #6	$216.72	12.664%	$244.1654	$244.17	$244.15	$244.20
Purchase #7	$72.47	8.314%	$78.4952	$78.50	$78.50	$78.50
7 purchase totals =	$911.45		$994.0180	$994.03	$994.00	$994.00