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	$163.91	4.313%	$170.9794	$170.98	$171.00	$171.00
Purchase #2	$216.86	12.447%	$243.8526	$243.85	$243.85	$243.90
Purchase #3	$144.76	4.645%	$151.4841	$151.48	$151.50	$151.50
Purchase #4	$40.88	6.528%	$43.5486	$43.55	$43.55	$43.50
Purchase #5	$182.45	7.150%	$195.4952	$195.50	$195.50	$195.50
Purchase #6	$184.54	4.111%	$192.1264	$192.13	$192.15	$192.10
Purchase #7	$230.56	12.155%	$258.5846	$258.58	$258.60	$258.60
7 purchase totals =	$1,163.96		$1,256.0709	$1,256.07	$1,256.15	$1,256.10