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	$187.65	10.191%	$206.7734	$206.77	$206.75	$206.80
Purchase #2	$81.44	6.453%	$86.6953	$86.70	$86.70	$86.70
Purchase #3	$169.59	8.503%	$184.0102	$184.01	$184.00	$184.00
Purchase #4	$54.49	3.574%	$56.4375	$56.44	$56.45	$56.40
Purchase #5	$199.33	11.632%	$222.5161	$222.52	$222.50	$222.50
Purchase #6	$111.61	13.706%	$126.9073	$126.91	$126.90	$126.90
Purchase #7	$144.61	7.451%	$155.3849	$155.38	$155.40	$155.40
7 purchase totals =	$948.72		$1,038.7247	$1,038.73	$1,038.70	$1,038.70