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	$208.30	4.810%	$218.3192	$218.32	$218.30	$218.30
Purchase #2	$129.37	9.782%	$142.025	$142.03	$142.05	$142.00
Purchase #3	$156.49	9.830%	$171.873	$171.87	$171.85	$171.90
Purchase #4	$69.38	10.406%	$76.5997	$76.60	$76.60	$76.60
Purchase #5	$126.57	4.205%	$131.8923	$131.89	$131.90	$131.90
Purchase #6	$227.37	9.612%	$249.2248	$249.22	$249.20	$249.20
Purchase #7	$236.33	9.574%	$258.9562	$258.96	$258.95	$259.00
7 purchase totals =	$1,153.81		$1,248.8902	$1,248.89	$1,248.85	$1,248.90