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	$143.95	4.853%	$150.9359	$150.94	$150.95	$150.90
Purchase #2	$173.47	9.520%	$189.9843	$189.98	$190.00	$190.00
Purchase #3	$39.70	8.386%	$43.0292	$43.03	$43.05	$43.00
Purchase #4	$23.92	5.340%	$25.1973	$25.20	$25.20	$25.20
Purchase #5	$95.36	11.561%	$106.3846	$106.38	$106.40	$106.40
Purchase #6	$125.37	4.585%	$131.1182	$131.12	$131.10	$131.10
Purchase #7	$162.95	6.449%	$173.4586	$173.46	$173.45	$173.50
7 purchase totals =	$764.72		$820.1081	$820.11	$820.15	$820.10