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	$165.72	6.765%	$176.931	$176.93	$176.95	$176.90
Purchase #2	$43.76	7.411%	$47.0031	$47.00	$47.00	$47.00
Purchase #3	$90.47	10.420%	$99.897	$99.90	$99.90	$99.90
Purchase #4	$92.68	9.499%	$101.4837	$101.48	$101.50	$101.50
Purchase #5	$207.33	12.689%	$233.6381	$233.64	$233.65	$233.60
Purchase #6	$189.35	11.683%	$211.4718	$211.47	$211.45	$211.50
Purchase #7	$99.78	3.169%	$102.942	$102.94	$102.95	$102.90
7 purchase totals =	$889.09		$973.3667	$973.36	$973.40	$973.30