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	$20.96	5.121%	$22.0334	$22.03	$22.05	$22.00
Purchase #2	$148.89	13.206%	$168.5524	$168.55	$168.55	$168.60
Purchase #3	$240.40	10.422%	$265.4545	$265.45	$265.45	$265.50
Purchase #4	$119.66	9.809%	$131.3974	$131.40	$131.40	$131.40
Purchase #5	$159.90	12.615%	$180.0714	$180.07	$180.05	$180.10
Purchase #6	$166.81	10.395%	$184.1499	$184.15	$184.15	$184.10
Purchase #7	$73.81	5.850%	$78.1279	$78.13	$78.15	$78.10
7 purchase totals =	$930.43		$1,029.7869	$1,029.78	$1,029.80	$1,029.80