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	$176.98	7.600%	$190.4305	$190.43	$190.45	$190.40
Purchase #2	$188.34	5.813%	$199.2882	$199.29	$199.30	$199.30
Purchase #3	$105.51	9.506%	$115.5398	$115.54	$115.55	$115.50
Purchase #4	$170.33	9.205%	$186.0089	$186.01	$186.00	$186.00
Purchase #5	$38.75	4.508%	$40.4969	$40.50	$40.50	$40.50
Purchase #6	$205.48	8.324%	$222.5842	$222.58	$222.60	$222.60
Purchase #7	$139.79	3.842%	$145.1607	$145.16	$145.15	$145.20
7 purchase totals =	$1,025.18		$1,099.5092	$1,099.51	$1,099.55	$1,099.50