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	$110.46	3.210%	$114.0058	$114.01	$114.00	$114.00
Purchase #2	$136.52	10.436%	$150.7672	$150.77	$150.75	$150.80
Purchase #3	$20.41	7.496%	$21.9399	$21.94	$21.95	$21.90
Purchase #4	$173.25	5.143%	$182.1602	$182.16	$182.15	$182.20
Purchase #5	$204.54	11.705%	$228.4814	$228.48	$228.50	$228.50
Purchase #6	$207.65	7.336%	$222.8832	$222.88	$222.90	$222.90
Purchase #7	$151.56	11.844%	$169.5108	$169.51	$169.50	$169.50
7 purchase totals =	$1,004.39		$1,089.7485	$1,089.75	$1,089.75	$1,089.80