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	$86.59	5.718%	$91.5412	$91.54	$91.55	$91.50
Purchase #2	$108.84	4.492%	$113.7291	$113.73	$113.75	$113.70
Purchase #3	$89.64	13.768%	$101.9816	$101.98	$102.00	$102.00
Purchase #4	$72.96	12.564%	$82.1267	$82.13	$82.15	$82.10
Purchase #5	$157.85	5.268%	$166.1655	$166.17	$166.15	$166.20
Purchase #6	$227.49	4.253%	$237.1651	$237.17	$237.15	$237.20
Purchase #7	$96.49	3.483%	$99.8507	$99.85	$99.85	$99.90
7 purchase totals =	$839.86		$892.5599	$892.57	$892.60	$892.60