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	$64.98	8.414%	$70.4474	$70.45	$70.45	$70.40
Purchase #2	$5.85	11.711%	$6.5351	$6.54	$6.55	$6.50
Purchase #3	$13.85	7.662%	$14.9112	$14.91	$14.90	$14.90
Purchase #4	$160.45	9.350%	$175.4521	$175.45	$175.45	$175.50
Purchase #5	$103.37	10.865%	$114.6012	$114.60	$114.60	$114.60
Purchase #6	$165.32	12.409%	$185.8346	$185.83	$185.85	$185.80
Purchase #7	$201.61	10.388%	$222.5532	$222.55	$222.55	$222.60
7 purchase totals =	$715.43		$790.3348	$790.33	$790.35	$790.30