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	$98.76	5.719%	$104.4081	$104.41	$104.40	$104.40
Purchase #2	$198.58	10.531%	$219.4925	$219.49	$219.50	$219.50
Purchase #3	$198.27	12.592%	$223.2362	$223.24	$223.25	$223.20
Purchase #4	$101.82	4.201%	$106.0975	$106.10	$106.10	$106.10
Purchase #5	$238.47	6.249%	$253.372	$253.37	$253.35	$253.40
Purchase #6	$208.53	6.208%	$221.4755	$221.48	$221.50	$221.50
Purchase #7	$36.79	9.599%	$40.3215	$40.32	$40.30	$40.30
7 purchase totals =	$1,081.22		$1,168.4033	$1,168.41	$1,168.40	$1,168.40