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	$32.62	11.762%	$36.4568	$36.46	$36.45	$36.50
Purchase #2	$86.78	8.267%	$93.9541	$93.95	$93.95	$94.00
Purchase #3	$213.69	11.788%	$238.8798	$238.88	$238.90	$238.90
Purchase #4	$128.48	9.389%	$140.543	$140.54	$140.55	$140.50
Purchase #5	$242.89	3.364%	$251.0608	$251.06	$251.05	$251.10
Purchase #6	$191.52	11.386%	$213.3265	$213.33	$213.35	$213.30
Purchase #7	$78.31	9.585%	$85.816	$85.82	$85.80	$85.80
7 purchase totals =	$974.29		$1,060.0370	$1,060.04	$1,060.05	$1,060.10