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	$111.29	7.423%	$119.5511	$119.55	$119.55	$119.60
Purchase #2	$59.33	10.221%	$65.3941	$65.39	$65.40	$65.40
Purchase #3	$131.34	9.371%	$143.6479	$143.65	$143.65	$143.60
Purchase #4	$146.54	7.348%	$157.3078	$157.31	$157.30	$157.30
Purchase #5	$206.31	10.142%	$227.234	$227.23	$227.25	$227.20
Purchase #6	$192.94	8.119%	$208.6048	$208.60	$208.60	$208.60
Purchase #7	$89.91	9.258%	$98.2339	$98.23	$98.25	$98.20
7 purchase totals =	$937.66		$1,019.9736	$1,019.96	$1,020.00	$1,019.90