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	$147.52	9.165%	$161.0402	$161.04	$161.05	$161.00
Purchase #2	$101.54	9.532%	$111.2188	$111.22	$111.20	$111.20
Purchase #3	$218.98	9.237%	$239.2072	$239.21	$239.20	$239.20
Purchase #4	$168.91	9.163%	$184.3872	$184.39	$184.40	$184.40
Purchase #5	$64.44	12.137%	$72.2611	$72.26	$72.25	$72.30
Purchase #6	$30.29	10.536%	$33.4814	$33.48	$33.50	$33.50
Purchase #7	$184.86	12.704%	$208.3446	$208.34	$208.35	$208.30
7 purchase totals =	$916.54		$1,009.9405	$1,009.94	$1,009.95	$1,009.90