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	$82.60	4.773%	$86.5425	$86.54	$86.55	$86.50
Purchase #2	$11.63	12.142%	$13.0421	$13.04	$13.05	$13.00
Purchase #3	$224.64	5.535%	$237.0738	$237.07	$237.05	$237.10
Purchase #4	$5.32	5.412%	$5.6079	$5.61	$5.60	$5.60
Purchase #5	$118.87	10.866%	$131.7864	$131.79	$131.80	$131.80
Purchase #6	$139.75	5.407%	$147.3063	$147.31	$147.30	$147.30
Purchase #7	$42.29	7.865%	$45.6161	$45.62	$45.60	$45.60
7 purchase totals =	$625.10		$666.9751	$666.98	$666.95	$666.90