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	$243.56	7.413%	$261.6151	$261.62	$261.60	$261.60
Purchase #2	$38.81	3.244%	$40.069	$40.07	$40.05	$40.10
Purchase #3	$64.47	13.660%	$73.2766	$73.28	$73.30	$73.30
Purchase #4	$210.58	9.174%	$229.8986	$229.90	$229.90	$229.90
Purchase #5	$59.59	12.807%	$67.2217	$67.22	$67.20	$67.20
Purchase #6	$151.41	7.603%	$162.9217	$162.92	$162.90	$162.90
Purchase #7	$146.93	13.595%	$166.9051	$166.91	$166.90	$166.90
7 purchase totals =	$915.35		$1,001.9078	$1,001.92	$1,001.85	$1,001.90