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	$214.31	7.383%	$230.1325	$230.13	$230.15	$230.10
Purchase #2	$174.73	9.257%	$190.9048	$190.90	$190.90	$190.90
Purchase #3	$51.52	13.758%	$58.6081	$58.61	$58.60	$58.60
Purchase #4	$54.65	8.161%	$59.11	$59.11	$59.10	$59.10
Purchase #5	$82.76	8.327%	$89.6514	$89.65	$89.65	$89.70
Purchase #6	$45.33	13.219%	$51.3222	$51.32	$51.30	$51.30
Purchase #7	$176.43	12.772%	$198.9636	$198.96	$198.95	$199.00
7 purchase totals =	$799.73		$878.6926	$878.68	$878.65	$878.70