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	$214.45	10.506%	$236.9801	$236.98	$237.00	$237.00
Purchase #2	$89.68	12.690%	$101.0604	$101.06	$101.05	$101.10
Purchase #3	$7.98	11.401%	$8.8898	$8.89	$8.90	$8.90
Purchase #4	$140.56	8.290%	$152.2124	$152.21	$152.20	$152.20
Purchase #5	$113.31	12.503%	$127.4771	$127.48	$127.50	$127.50
Purchase #6	$21.43	12.361%	$24.079	$24.08	$24.10	$24.10
Purchase #7	$34.93	9.145%	$38.1243	$38.12	$38.10	$38.10
7 purchase totals =	$622.34		$688.8231	$688.82	$688.85	$688.90