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	$149.27	5.452%	$157.4082	$157.41	$157.40	$157.40
Purchase #2	$44.41	4.699%	$46.4968	$46.50	$46.50	$46.50
Purchase #3	$171.31	9.337%	$187.3052	$187.31	$187.30	$187.30
Purchase #4	$54.36	8.562%	$59.0143	$59.01	$59.00	$59.00
Purchase #5	$26.51	6.126%	$28.134	$28.13	$28.15	$28.10
Purchase #6	$216.98	10.649%	$240.0862	$240.09	$240.10	$240.10
Purchase #7	$84.99	5.192%	$89.4027	$89.40	$89.40	$89.40
7 purchase totals =	$747.83		$807.8474	$807.85	$807.85	$807.80