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	$103.49	3.459%	$107.0697	$107.07	$107.05	$107.10
Purchase #2	$99.53	12.252%	$111.7244	$111.72	$111.70	$111.70
Purchase #3	$137.49	7.476%	$147.7688	$147.77	$147.75	$147.80
Purchase #4	$66.95	8.849%	$72.8744	$72.87	$72.85	$72.90
Purchase #5	$160.80	5.645%	$169.8772	$169.88	$169.90	$169.90
Purchase #6	$117.38	4.870%	$123.0964	$123.10	$123.10	$123.10
Purchase #7	$228.41	5.180%	$240.2416	$240.24	$240.25	$240.20
7 purchase totals =	$914.05		$972.6525	$972.65	$972.60	$972.70