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	$167.87	8.784%	$182.6157	$182.62	$182.60	$182.60
Purchase #2	$139.50	7.800%	$150.381	$150.38	$150.40	$150.40
Purchase #3	$157.55	13.727%	$179.1769	$179.18	$179.20	$179.20
Purchase #4	$127.36	13.436%	$144.4721	$144.47	$144.45	$144.50
Purchase #5	$157.74	3.139%	$162.6915	$162.69	$162.70	$162.70
Purchase #6	$201.76	13.507%	$229.0117	$229.01	$229.00	$229.00
Purchase #7	$96.44	9.469%	$105.5719	$105.57	$105.55	$105.60
7 purchase totals =	$1,048.22		$1,153.9208	$1,153.92	$1,153.90	$1,154.00