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	$165.49	5.638%	$174.8203	$174.82	$174.80	$174.80
Purchase #2	$80.28	11.211%	$89.2802	$89.28	$89.30	$89.30
Purchase #3	$6.76	9.776%	$7.4209	$7.42	$7.40	$7.40
Purchase #4	$85.60	7.621%	$92.1236	$92.12	$92.10	$92.10
Purchase #5	$126.59	9.357%	$138.435	$138.44	$138.45	$138.40
Purchase #6	$58.69	12.201%	$65.8508	$65.85	$65.85	$65.90
Purchase #7	$128.68	10.695%	$142.4423	$142.44	$142.45	$142.40
7 purchase totals =	$652.09		$710.3731	$710.37	$710.35	$710.30