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	$156.63	5.478%	$165.2102	$165.21	$165.20	$165.20
Purchase #2	$56.45	12.265%	$63.3736	$63.37	$63.35	$63.40
Purchase #3	$151.89	11.475%	$169.3194	$169.32	$169.30	$169.30
Purchase #4	$103.43	11.761%	$115.5944	$115.59	$115.60	$115.60
Purchase #5	$188.64	5.365%	$198.7605	$198.76	$198.75	$198.80
Purchase #6	$175.35	12.175%	$196.6989	$196.70	$196.70	$196.70
Purchase #7	$192.84	8.121%	$208.5005	$208.50	$208.50	$208.50
7 purchase totals =	$1,025.23		$1,117.4575	$1,117.45	$1,117.40	$1,117.50