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	$94.66	10.149%	$104.267	$104.27	$104.25	$104.30
Purchase #2	$215.56	9.466%	$235.9649	$235.96	$235.95	$236.00
Purchase #3	$171.39	6.647%	$182.7823	$182.78	$182.80	$182.80
Purchase #4	$225.59	12.402%	$253.5677	$253.57	$253.55	$253.60
Purchase #5	$72.92	5.421%	$76.873	$76.87	$76.85	$76.90
Purchase #6	$245.27	4.204%	$255.5812	$255.58	$255.60	$255.60
Purchase #7	$165.38	4.466%	$172.7659	$172.77	$172.75	$172.80
7 purchase totals =	$1,190.77		$1,281.8020	$1,281.80	$1,281.75	$1,282.00