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	$116.84	13.482%	$132.5924	$132.59	$132.60	$132.60
Purchase #2	$63.59	3.707%	$65.9473	$65.95	$65.95	$65.90
Purchase #3	$209.52	5.196%	$220.4067	$220.41	$220.40	$220.40
Purchase #4	$114.56	8.437%	$124.2254	$124.23	$124.25	$124.20
Purchase #5	$216.55	12.313%	$243.2138	$243.21	$243.20	$243.20
Purchase #6	$84.48	6.747%	$90.1799	$90.18	$90.20	$90.20
Purchase #7	$156.67	7.812%	$168.9091	$168.91	$168.90	$168.90
7 purchase totals =	$962.21		$1,045.4746	$1,045.48	$1,045.50	$1,045.40