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	$134.83	9.701%	$147.9099	$147.91	$147.90	$147.90
Purchase #2	$134.89	11.609%	$150.5494	$150.55	$150.55	$150.50
Purchase #3	$55.80	5.856%	$59.0676	$59.07	$59.05	$59.10
Purchase #4	$232.79	9.578%	$255.0866	$255.09	$255.10	$255.10
Purchase #5	$160.31	3.174%	$165.3982	$165.40	$165.40	$165.40
Purchase #6	$230.66	3.338%	$238.3594	$238.36	$238.35	$238.40
Purchase #7	$47.63	9.155%	$51.9905	$51.99	$52.00	$52.00
7 purchase totals =	$996.91		$1,068.3616	$1,068.37	$1,068.35	$1,068.40