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	$171.87	10.524%	$189.9576	$189.96	$189.95	$190.00
Purchase #2	$48.87	9.730%	$53.6251	$53.63	$53.65	$53.60
Purchase #3	$194.41	11.338%	$216.4522	$216.45	$216.45	$216.50
Purchase #4	$77.29	7.343%	$82.9654	$82.97	$82.95	$83.00
Purchase #5	$160.34	6.656%	$171.0122	$171.01	$171.00	$171.00
Purchase #6	$45.71	11.446%	$50.942	$50.94	$50.95	$50.90
Purchase #7	$217.59	11.510%	$242.6346	$242.63	$242.65	$242.60
7 purchase totals =	$916.08		$1,007.5891	$1,007.59	$1,007.60	$1,007.60