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	$180.70	5.593%	$190.8066	$190.81	$190.80	$190.80
Purchase #2	$189.85	11.119%	$210.9594	$210.96	$210.95	$211.00
Purchase #3	$217.37	6.421%	$231.3273	$231.33	$231.35	$231.30
Purchase #4	$201.80	7.118%	$216.1641	$216.16	$216.15	$216.20
Purchase #5	$39.89	6.694%	$42.5602	$42.56	$42.55	$42.60
Purchase #6	$211.71	10.724%	$234.4138	$234.41	$234.40	$234.40
Purchase #7	$117.55	9.724%	$128.9806	$128.98	$129.00	$129.00
7 purchase totals =	$1,158.87		$1,255.2120	$1,255.21	$1,255.20	$1,255.30