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	$64.80	10.700%	$71.7336	$71.73	$71.75	$71.70
Purchase #2	$82.57	6.508%	$87.9437	$87.94	$87.95	$87.90
Purchase #3	$63.40	4.325%	$66.1421	$66.14	$66.15	$66.10
Purchase #4	$103.33	7.856%	$111.4476	$111.45	$111.45	$111.40
Purchase #5	$162.90	10.755%	$180.4199	$180.42	$180.40	$180.40
Purchase #6	$193.99	9.607%	$212.6266	$212.63	$212.65	$212.60
Purchase #7	$25.72	6.372%	$27.3589	$27.36	$27.35	$27.40
7 purchase totals =	$696.71		$757.6724	$757.67	$757.70	$757.50