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	$86.80	9.589%	$95.1233	$95.12	$95.10	$95.10
Purchase #2	$68.87	3.202%	$71.0752	$71.08	$71.10	$71.10
Purchase #3	$138.58	11.694%	$154.7855	$154.79	$154.80	$154.80
Purchase #4	$172.56	6.630%	$184.0007	$184.00	$184.00	$184.00
Purchase #5	$72.46	7.858%	$78.1539	$78.15	$78.15	$78.20
Purchase #6	$64.67	11.517%	$72.118	$72.12	$72.10	$72.10
Purchase #7	$140.83	9.802%	$154.6342	$154.63	$154.65	$154.60
7 purchase totals =	$744.77		$809.8908	$809.89	$809.90	$809.90