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	$79.92	3.465%	$82.6892	$82.69	$82.70	$82.70
Purchase #2	$102.59	8.601%	$111.4138	$111.41	$111.40	$111.40
Purchase #3	$163.35	5.308%	$172.0206	$172.02	$172.00	$172.00
Purchase #4	$243.43	6.156%	$258.4156	$258.42	$258.40	$258.40
Purchase #5	$207.70	6.152%	$220.4777	$220.48	$220.50	$220.50
Purchase #6	$140.57	8.661%	$152.7448	$152.74	$152.75	$152.70
Purchase #7	$105.96	5.643%	$111.9393	$111.94	$111.95	$111.90
7 purchase totals =	$1,043.52		$1,109.7010	$1,109.70	$1,109.70	$1,109.60