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	$118.93	9.841%	$130.6339	$130.63	$130.65	$130.60
Purchase #2	$41.91	3.806%	$43.5051	$43.51	$43.50	$43.50
Purchase #3	$36.38	8.172%	$39.353	$39.35	$39.35	$39.40
Purchase #4	$245.83	11.151%	$273.2425	$273.24	$273.25	$273.20
Purchase #5	$166.29	5.252%	$175.0236	$175.02	$175.00	$175.00
Purchase #6	$167.89	8.117%	$181.5176	$181.52	$181.50	$181.50
Purchase #7	$224.91	4.315%	$234.6149	$234.61	$234.60	$234.60
7 purchase totals =	$1,002.14		$1,077.8906	$1,077.88	$1,077.85	$1,077.80