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	$10.65	6.394%	$11.331	$11.33	$11.35	$11.30
Purchase #2	$161.33	12.467%	$181.443	$181.44	$181.45	$181.40
Purchase #3	$220.28	6.413%	$234.4066	$234.41	$234.40	$234.40
Purchase #4	$174.76	3.785%	$181.3747	$181.37	$181.35	$181.40
Purchase #5	$52.38	13.638%	$59.5236	$59.52	$59.50	$59.50
Purchase #6	$68.25	12.585%	$76.8393	$76.84	$76.85	$76.80
Purchase #7	$222.72	8.409%	$241.4485	$241.45	$241.45	$241.40
7 purchase totals =	$910.37		$986.3667	$986.36	$986.35	$986.20