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	$181.85	12.680%	$204.9086	$204.91	$204.90	$204.90
Purchase #2	$93.88	11.871%	$105.0245	$105.02	$105.00	$105.00
Purchase #3	$139.41	5.871%	$147.5948	$147.59	$147.60	$147.60
Purchase #4	$58.96	11.585%	$65.7905	$65.79	$65.80	$65.80
Purchase #5	$51.42	5.533%	$54.2651	$54.27	$54.25	$54.30
Purchase #6	$128.55	6.467%	$136.8633	$136.86	$136.85	$136.90
Purchase #7	$20.74	4.153%	$21.6013	$21.60	$21.60	$21.60
7 purchase totals =	$674.81		$736.0481	$736.04	$736.00	$736.10