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	$83.27	7.506%	$89.5202	$89.52	$89.50	$89.50
Purchase #2	$165.49	4.112%	$172.2949	$172.29	$172.30	$172.30
Purchase #3	$156.89	13.860%	$178.635	$178.64	$178.65	$178.60
Purchase #4	$178.67	7.803%	$192.6116	$192.61	$192.60	$192.60
Purchase #5	$8.98	4.427%	$9.3775	$9.38	$9.40	$9.40
Purchase #6	$34.93	12.612%	$39.3354	$39.34	$39.35	$39.30
Purchase #7	$77.57	11.346%	$86.3711	$86.37	$86.35	$86.40
7 purchase totals =	$705.80		$768.1457	$768.15	$768.15	$768.10