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	$207.69	7.740%	$223.7652	$223.77	$223.75	$223.80
Purchase #2	$116.55	10.128%	$128.3542	$128.35	$128.35	$128.40
Purchase #3	$180.84	4.295%	$188.6071	$188.61	$188.60	$188.60
Purchase #4	$84.56	7.480%	$90.8851	$90.89	$90.90	$90.90
Purchase #5	$69.30	6.226%	$73.6146	$73.61	$73.60	$73.60
Purchase #6	$125.98	12.402%	$141.604	$141.60	$141.60	$141.60
Purchase #7	$176.96	7.137%	$189.5896	$189.59	$189.60	$189.60
7 purchase totals =	$961.88		$1,036.4198	$1,036.42	$1,036.40	$1,036.50