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	$94.56	8.270%	$102.3801	$102.38	$102.40	$102.40
Purchase #2	$158.61	7.762%	$170.9213	$170.92	$170.90	$170.90
Purchase #3	$89.32	3.162%	$92.1443	$92.14	$92.15	$92.10
Purchase #4	$92.43	3.205%	$95.3924	$95.39	$95.40	$95.40
Purchase #5	$112.52	12.459%	$126.5389	$126.54	$126.55	$126.50
Purchase #6	$215.80	3.583%	$223.5321	$223.53	$223.55	$223.50
Purchase #7	$210.92	6.687%	$225.0242	$225.02	$225.00	$225.00
7 purchase totals =	$974.16		$1,035.9333	$1,035.92	$1,035.95	$1,035.80