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	$100.40	11.429%	$111.8747	$111.87	$111.85	$111.90
Purchase #2	$82.46	10.344%	$90.9897	$90.99	$91.00	$91.00
Purchase #3	$244.33	7.418%	$262.4544	$262.45	$262.45	$262.50
Purchase #4	$87.84	11.408%	$97.8608	$97.86	$97.85	$97.90
Purchase #5	$224.60	6.323%	$238.8015	$238.80	$238.80	$238.80
Purchase #6	$120.85	6.427%	$128.617	$128.62	$128.60	$128.60
Purchase #7	$96.87	13.488%	$109.9358	$109.94	$109.95	$109.90
7 purchase totals =	$957.35		$1,040.5339	$1,040.53	$1,040.50	$1,040.60