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	$51.98	13.547%	$59.0217	$59.02	$59.00	$59.00
Purchase #2	$132.67	11.864%	$148.41	$148.41	$148.40	$148.40
Purchase #3	$80.79	10.545%	$89.3093	$89.31	$89.30	$89.30
Purchase #4	$63.51	7.163%	$68.0592	$68.06	$68.05	$68.10
Purchase #5	$53.39	11.474%	$59.516	$59.52	$59.50	$59.50
Purchase #6	$238.40	8.494%	$258.6497	$258.65	$258.65	$258.60
Purchase #7	$122.47	6.454%	$130.3742	$130.37	$130.35	$130.40
7 purchase totals =	$743.21		$813.3401	$813.34	$813.25	$813.30