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	$157.86	10.735%	$174.8063	$174.81	$174.80	$174.80
Purchase #2	$54.71	9.173%	$59.7285	$59.73	$59.75	$59.70
Purchase #3	$133.93	3.354%	$138.422	$138.42	$138.40	$138.40
Purchase #4	$13.39	7.582%	$14.4052	$14.41	$14.40	$14.40
Purchase #5	$195.53	5.703%	$206.6811	$206.68	$206.70	$206.70
Purchase #6	$64.86	11.730%	$72.4681	$72.47	$72.45	$72.50
Purchase #7	$88.51	12.579%	$99.6437	$99.64	$99.65	$99.60
7 purchase totals =	$708.79		$766.1549	$766.16	$766.15	$766.10