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	$190.46	9.810%	$209.1441	$209.14	$209.15	$209.10
Purchase #2	$170.37	9.160%	$185.9759	$185.98	$186.00	$186.00
Purchase #3	$216.61	12.245%	$243.1339	$243.13	$243.15	$243.10
Purchase #4	$199.59	9.196%	$217.9443	$217.94	$217.95	$217.90
Purchase #5	$56.56	4.603%	$59.1635	$59.16	$59.15	$59.20
Purchase #6	$59.64	12.833%	$67.2936	$67.29	$67.30	$67.30
Purchase #7	$77.36	8.564%	$83.9851	$83.99	$84.00	$84.00
7 purchase totals =	$970.59		$1,066.6404	$1,066.63	$1,066.70	$1,066.60