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	$194.30	3.297%	$200.7061	$200.71	$200.70	$200.70
Purchase #2	$91.51	6.813%	$97.7446	$97.74	$97.75	$97.70
Purchase #3	$33.64	7.138%	$36.0412	$36.04	$36.05	$36.00
Purchase #4	$115.93	6.481%	$123.4434	$123.44	$123.45	$123.40
Purchase #5	$169.93	9.141%	$185.4633	$185.46	$185.45	$185.50
Purchase #6	$185.42	8.160%	$200.5503	$200.55	$200.55	$200.60
Purchase #7	$133.33	12.611%	$150.1442	$150.14	$150.15	$150.10
7 purchase totals =	$924.06		$994.0931	$994.08	$994.10	$994.00