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	$88.92	13.253%	$100.7046	$100.70	$100.70	$100.70
Purchase #2	$167.95	9.178%	$183.3645	$183.36	$183.35	$183.40
Purchase #3	$111.30	4.748%	$116.5845	$116.58	$116.60	$116.60
Purchase #4	$85.48	7.506%	$91.8961	$91.90	$91.90	$91.90
Purchase #5	$237.31	3.650%	$245.9718	$245.97	$245.95	$246.00
Purchase #6	$157.83	6.375%	$167.8917	$167.89	$167.90	$167.90
Purchase #7	$60.53	7.180%	$64.8761	$64.88	$64.90	$64.90
7 purchase totals =	$909.32		$971.2893	$971.28	$971.30	$971.40