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	$185.38	8.311%	$200.7869	$200.79	$200.80	$200.80
Purchase #2	$140.59	11.516%	$156.7803	$156.78	$156.80	$156.80
Purchase #3	$68.52	4.396%	$71.5321	$71.53	$71.55	$71.50
Purchase #4	$54.80	3.302%	$56.6095	$56.61	$56.60	$56.60
Purchase #5	$212.32	3.597%	$219.9572	$219.96	$219.95	$220.00
Purchase #6	$120.29	7.750%	$129.6125	$129.61	$129.60	$129.60
Purchase #7	$178.65	12.317%	$200.6543	$200.65	$200.65	$200.70
7 purchase totals =	$960.55		$1,035.9328	$1,035.93	$1,035.95	$1,036.00