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	$82.95	11.112%	$92.1674	$92.17	$92.15	$92.20
Purchase #2	$80.52	7.561%	$86.6081	$86.61	$86.60	$86.60
Purchase #3	$28.47	9.305%	$31.1191	$31.12	$31.10	$31.10
Purchase #4	$230.78	10.867%	$255.8589	$255.86	$255.85	$255.90
Purchase #5	$34.68	10.764%	$38.413	$38.41	$38.40	$38.40
Purchase #6	$98.66	4.576%	$103.1747	$103.17	$103.15	$103.20
Purchase #7	$212.28	13.855%	$241.6914	$241.69	$241.70	$241.70
7 purchase totals =	$768.34		$849.0326	$849.03	$848.95	$849.10