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	$181.35	6.557%	$193.2411	$193.24	$193.25	$193.20
Purchase #2	$150.99	12.258%	$169.4984	$169.50	$169.50	$169.50
Purchase #3	$135.30	12.650%	$152.4155	$152.42	$152.40	$152.40
Purchase #4	$176.75	7.505%	$190.0151	$190.02	$190.00	$190.00
Purchase #5	$38.78	12.664%	$43.6911	$43.69	$43.70	$43.70
Purchase #6	$172.36	13.841%	$196.2163	$196.22	$196.20	$196.20
Purchase #7	$127.83	6.396%	$136.006	$136.01	$136.00	$136.00
7 purchase totals =	$983.36		$1,081.0835	$1,081.10	$1,081.05	$1,081.00