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	$191.96	4.446%	$200.4945	$200.49	$200.50	$200.50
Purchase #2	$226.93	10.201%	$250.0791	$250.08	$250.10	$250.10
Purchase #3	$79.34	9.591%	$86.9495	$86.95	$86.95	$86.90
Purchase #4	$235.96	11.252%	$262.5102	$262.51	$262.50	$262.50
Purchase #5	$61.28	6.313%	$65.1486	$65.15	$65.15	$65.10
Purchase #6	$73.63	4.445%	$76.9029	$76.90	$76.90	$76.90
Purchase #7	$176.76	7.213%	$189.5097	$189.51	$189.50	$189.50
7 purchase totals =	$1,045.86		$1,131.5945	$1,131.59	$1,131.60	$1,131.50