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	$67.83	13.187%	$76.7747	$76.77	$76.75	$76.80
Purchase #2	$162.80	5.280%	$171.3958	$171.40	$171.40	$171.40
Purchase #3	$200.56	9.567%	$219.7476	$219.75	$219.75	$219.70
Purchase #4	$232.26	8.250%	$251.4215	$251.42	$251.40	$251.40
Purchase #5	$55.61	6.182%	$59.0478	$59.05	$59.05	$59.00
Purchase #6	$23.31	9.679%	$25.5662	$25.57	$25.55	$25.60
Purchase #7	$183.88	9.254%	$200.8963	$200.90	$200.90	$200.90
7 purchase totals =	$926.25		$1,004.8499	$1,004.86	$1,004.80	$1,004.80