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	$215.34	7.614%	$231.736	$231.74	$231.75	$231.70
Purchase #2	$166.36	8.195%	$179.9932	$179.99	$180.00	$180.00
Purchase #3	$79.38	12.816%	$89.5533	$89.55	$89.55	$89.60
Purchase #4	$73.57	11.614%	$82.1144	$82.11	$82.10	$82.10
Purchase #5	$99.47	3.415%	$102.8669	$102.87	$102.85	$102.90
Purchase #6	$108.64	4.369%	$113.3865	$113.39	$113.40	$113.40
Purchase #7	$76.99	11.540%	$85.8746	$85.87	$85.85	$85.90
7 purchase totals =	$819.75		$885.5249	$885.52	$885.50	$885.60