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	$152.36	11.476%	$169.8448	$169.84	$169.85	$169.80
Purchase #2	$74.88	4.297%	$78.0976	$78.10	$78.10	$78.10
Purchase #3	$37.25	4.758%	$39.0224	$39.02	$39.00	$39.00
Purchase #4	$82.37	5.643%	$87.0181	$87.02	$87.00	$87.00
Purchase #5	$46.99	13.545%	$53.3548	$53.35	$53.35	$53.40
Purchase #6	$169.51	12.409%	$190.5445	$190.54	$190.55	$190.50
Purchase #7	$39.63	7.745%	$42.6993	$42.70	$42.70	$42.70
7 purchase totals =	$602.99		$660.5815	$660.57	$660.55	$660.50