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	$124.95	13.658%	$142.0157	$142.02	$142.00	$142.00
Purchase #2	$95.48	11.598%	$106.5538	$106.55	$106.55	$106.60
Purchase #3	$106.26	3.303%	$109.7698	$109.77	$109.75	$109.80
Purchase #4	$182.84	4.154%	$190.4352	$190.44	$190.45	$190.40
Purchase #5	$209.54	10.509%	$231.5606	$231.56	$231.55	$231.60
Purchase #6	$152.89	4.140%	$159.2196	$159.22	$159.20	$159.20
Purchase #7	$205.81	11.348%	$229.1653	$229.17	$229.15	$229.20
7 purchase totals =	$1,077.77		$1,168.7200	$1,168.73	$1,168.65	$1,168.80