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	$167.94	7.796%	$181.0326	$181.03	$181.05	$181.00
Purchase #2	$135.39	7.406%	$145.417	$145.42	$145.40	$145.40
Purchase #3	$210.51	11.174%	$234.0324	$234.03	$234.05	$234.00
Purchase #4	$118.42	11.139%	$131.6108	$131.61	$131.60	$131.60
Purchase #5	$109.70	7.812%	$118.2698	$118.27	$118.25	$118.30
Purchase #6	$92.96	5.514%	$98.0858	$98.09	$98.10	$98.10
Purchase #7	$83.79	6.638%	$89.352	$89.35	$89.35	$89.40
7 purchase totals =	$918.71		$997.8004	$997.80	$997.80	$997.80