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	$192.90	11.740%	$215.5465	$215.55	$215.55	$215.50
Purchase #2	$84.39	12.288%	$94.7598	$94.76	$94.75	$94.80
Purchase #3	$183.47	3.532%	$189.9502	$189.95	$189.95	$190.00
Purchase #4	$135.37	9.523%	$148.2613	$148.26	$148.25	$148.30
Purchase #5	$225.42	13.803%	$256.5347	$256.53	$256.55	$256.50
Purchase #6	$50.57	9.447%	$55.3473	$55.35	$55.35	$55.30
Purchase #7	$156.57	7.435%	$168.211	$168.21	$168.20	$168.20
7 purchase totals =	$1,028.69		$1,128.6108	$1,128.61	$1,128.60	$1,128.60