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	$152.47	7.788%	$164.3444	$164.34	$164.35	$164.30
Purchase #2	$198.29	3.136%	$204.5084	$204.51	$204.50	$204.50
Purchase #3	$106.47	12.503%	$119.7819	$119.78	$119.80	$119.80
Purchase #4	$132.75	6.302%	$141.1159	$141.12	$141.10	$141.10
Purchase #5	$237.46	9.285%	$259.5082	$259.51	$259.50	$259.50
Purchase #6	$84.38	5.542%	$89.0563	$89.06	$89.05	$89.10
Purchase #7	$48.39	12.830%	$54.5984	$54.60	$54.60	$54.60
7 purchase totals =	$960.21		$1,032.9135	$1,032.92	$1,032.90	$1,032.90