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	$140.94	8.182%	$152.4717	$152.47	$152.45	$152.50
Purchase #2	$178.37	4.159%	$185.7884	$185.79	$185.80	$185.80
Purchase #3	$194.54	12.818%	$219.4761	$219.48	$219.50	$219.50
Purchase #4	$135.87	12.527%	$152.8904	$152.89	$152.90	$152.90
Purchase #5	$183.48	13.279%	$207.8443	$207.84	$207.85	$207.80
Purchase #6	$106.67	4.251%	$111.2045	$111.20	$111.20	$111.20
Purchase #7	$62.71	11.627%	$70.0013	$70.00	$70.00	$70.00
7 purchase totals =	$1,002.58		$1,099.6767	$1,099.67	$1,099.70	$1,099.70