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	$245.82	9.442%	$269.0303	$269.03	$269.05	$269.00
Purchase #2	$135.62	6.551%	$144.5045	$144.50	$144.50	$144.50
Purchase #3	$77.74	9.369%	$85.0235	$85.02	$85.00	$85.00
Purchase #4	$148.75	7.278%	$159.576	$159.58	$159.60	$159.60
Purchase #5	$175.62	9.545%	$192.3829	$192.38	$192.40	$192.40
Purchase #6	$103.32	4.411%	$107.8774	$107.88	$107.90	$107.90
Purchase #7	$78.99	13.259%	$89.4633	$89.46	$89.45	$89.50
7 purchase totals =	$965.86		$1,047.8579	$1,047.85	$1,047.90	$1,047.90