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	$164.45	12.650%	$185.2529	$185.25	$185.25	$185.30
Purchase #2	$147.85	6.147%	$156.9383	$156.94	$156.95	$156.90
Purchase #3	$87.34	5.174%	$91.859	$91.86	$91.85	$91.90
Purchase #4	$153.52	7.873%	$165.6066	$165.61	$165.60	$165.60
Purchase #5	$146.26	12.756%	$164.9169	$164.92	$164.90	$164.90
Purchase #6	$93.49	7.152%	$100.1764	$100.18	$100.20	$100.20
Purchase #7	$191.64	10.495%	$211.7526	$211.75	$211.75	$211.80
7 purchase totals =	$984.55		$1,076.5027	$1,076.51	$1,076.50	$1,076.60