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	$103.95	9.426%	$113.7483	$113.75	$113.75	$113.70
Purchase #2	$142.81	4.270%	$148.908	$148.91	$148.90	$148.90
Purchase #3	$224.48	13.741%	$255.3258	$255.33	$255.35	$255.30
Purchase #4	$18.35	11.383%	$20.4388	$20.44	$20.45	$20.40
Purchase #5	$137.38	10.697%	$152.0755	$152.08	$152.10	$152.10
Purchase #6	$173.40	6.612%	$184.8652	$184.87	$184.85	$184.90
Purchase #7	$93.27	11.169%	$103.6873	$103.69	$103.70	$103.70
7 purchase totals =	$893.64		$979.0489	$979.07	$979.10	$979.00