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	$136.40	11.104%	$151.5459	$151.55	$151.55	$151.50
Purchase #2	$196.76	8.873%	$214.2185	$214.22	$214.20	$214.20
Purchase #3	$79.48	11.426%	$88.5614	$88.56	$88.55	$88.60
Purchase #4	$99.61	6.164%	$105.75	$105.75	$105.75	$105.80
Purchase #5	$169.63	8.689%	$184.3692	$184.37	$184.35	$184.40
Purchase #6	$99.96	10.630%	$110.5857	$110.59	$110.60	$110.60
Purchase #7	$185.52	8.310%	$200.9367	$200.94	$200.95	$200.90
7 purchase totals =	$967.36		$1,055.9674	$1,055.98	$1,055.95	$1,056.00