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	$72.31	13.603%	$82.1463	$82.15	$82.15	$82.10
Purchase #2	$18.35	5.380%	$19.3372	$19.34	$19.35	$19.30
Purchase #3	$128.96	9.598%	$141.3376	$141.34	$141.35	$141.30
Purchase #4	$32.85	9.109%	$35.8423	$35.84	$35.85	$35.80
Purchase #5	$26.68	11.188%	$29.665	$29.67	$29.65	$29.70
Purchase #6	$40.90	4.300%	$42.6587	$42.66	$42.65	$42.70
Purchase #7	$86.99	12.122%	$97.5349	$97.53	$97.55	$97.50
7 purchase totals =	$407.04		$448.5220	$448.53	$448.55	$448.40