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	$118.92	10.507%	$131.4149	$131.41	$131.40	$131.40
Purchase #2	$32.33	3.797%	$33.5576	$33.56	$33.55	$33.60
Purchase #3	$247.43	3.310%	$255.6199	$255.62	$255.60	$255.60
Purchase #4	$245.45	5.248%	$258.3312	$258.33	$258.35	$258.30
Purchase #5	$88.56	3.852%	$91.9713	$91.97	$91.95	$92.00
Purchase #6	$234.45	5.768%	$247.9731	$247.97	$247.95	$248.00
Purchase #7	$117.68	11.788%	$131.5521	$131.55	$131.55	$131.60
7 purchase totals =	$1,084.82		$1,150.4201	$1,150.41	$1,150.35	$1,150.50