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	$111.38	10.466%	$123.037	$123.04	$123.05	$123.00
Purchase #2	$162.76	7.441%	$174.871	$174.87	$174.85	$174.90
Purchase #3	$95.86	13.797%	$109.0858	$109.09	$109.10	$109.10
Purchase #4	$128.54	10.144%	$141.5791	$141.58	$141.60	$141.60
Purchase #5	$31.88	11.412%	$35.5181	$35.52	$35.50	$35.50
Purchase #6	$28.37	11.492%	$31.6303	$31.63	$31.65	$31.60
Purchase #7	$79.70	5.580%	$84.1473	$84.15	$84.15	$84.10
7 purchase totals =	$638.49		$699.8686	$699.88	$699.90	$699.80