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	$143.42	13.354%	$162.5723	$162.57	$162.55	$162.60
Purchase #2	$204.35	6.432%	$217.4938	$217.49	$217.50	$217.50
Purchase #3	$211.45	8.721%	$229.8906	$229.89	$229.90	$229.90
Purchase #4	$79.81	4.787%	$83.6305	$83.63	$83.65	$83.60
Purchase #5	$34.25	10.309%	$37.7808	$37.78	$37.80	$37.80
Purchase #6	$52.25	10.698%	$57.8397	$57.84	$57.85	$57.80
Purchase #7	$89.91	9.530%	$98.4784	$98.48	$98.50	$98.50
7 purchase totals =	$815.44		$887.6861	$887.68	$887.75	$887.70