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	$101.96	9.104%	$111.2424	$111.24	$111.25	$111.20
Purchase #2	$6.91	7.266%	$7.4121	$7.41	$7.40	$7.40
Purchase #3	$218.79	6.752%	$233.5627	$233.56	$233.55	$233.60
Purchase #4	$80.78	8.213%	$87.4145	$87.41	$87.40	$87.40
Purchase #5	$188.46	5.698%	$199.1985	$199.20	$199.20	$199.20
Purchase #6	$107.76	3.684%	$111.7299	$111.73	$111.75	$111.70
Purchase #7	$229.44	13.336%	$260.0381	$260.04	$260.05	$260.00
7 purchase totals =	$934.10		$1,010.5982	$1,010.59	$1,010.60	$1,010.50