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	$111.71	4.620%	$116.871	$116.87	$116.85	$116.90
Purchase #2	$78.64	10.245%	$86.6967	$86.70	$86.70	$86.70
Purchase #3	$93.31	9.856%	$102.5066	$102.51	$102.50	$102.50
Purchase #4	$41.99	7.849%	$45.2858	$45.29	$45.30	$45.30
Purchase #5	$18.89	9.524%	$20.6891	$20.69	$20.70	$20.70
Purchase #6	$28.92	4.864%	$30.3267	$30.33	$30.35	$30.30
Purchase #7	$44.93	10.427%	$49.6149	$49.61	$49.60	$49.60
7 purchase totals =	$418.39		$451.9908	$452.00	$452.00	$452.00