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	$173.35	13.392%	$196.565	$196.57	$196.55	$196.60
Purchase #2	$156.89	11.695%	$175.2383	$175.24	$175.25	$175.20
Purchase #3	$226.53	12.500%	$254.8463	$254.85	$254.85	$254.80
Purchase #4	$54.64	3.363%	$56.4775	$56.48	$56.50	$56.50
Purchase #5	$81.81	5.642%	$86.4257	$86.43	$86.45	$86.40
Purchase #6	$215.35	6.111%	$228.51	$228.51	$228.50	$228.50
Purchase #7	$157.46	7.148%	$168.7152	$168.72	$168.70	$168.70
7 purchase totals =	$1,066.03		$1,166.7780	$1,166.80	$1,166.80	$1,166.70