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	$199.89	11.116%	$222.1098	$222.11	$222.10	$222.10
Purchase #2	$64.79	13.345%	$73.4362	$73.44	$73.45	$73.40
Purchase #3	$190.33	5.362%	$200.5355	$200.54	$200.55	$200.50
Purchase #4	$23.47	8.638%	$25.4973	$25.50	$25.50	$25.50
Purchase #5	$143.73	13.109%	$162.5716	$162.57	$162.55	$162.60
Purchase #6	$160.87	10.516%	$177.7871	$177.79	$177.80	$177.80
Purchase #7	$242.82	13.537%	$275.6905	$275.69	$275.70	$275.70
7 purchase totals =	$1,025.90		$1,137.6280	$1,137.64	$1,137.65	$1,137.60