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	$136.70	12.181%	$153.3514	$153.35	$153.35	$153.40
Purchase #2	$201.88	3.680%	$209.3092	$209.31	$209.30	$209.30
Purchase #3	$85.69	5.280%	$90.2144	$90.21	$90.20	$90.20
Purchase #4	$86.32	4.201%	$89.9463	$89.95	$89.95	$89.90
Purchase #5	$111.61	8.116%	$120.6683	$120.67	$120.65	$120.70
Purchase #6	$225.55	5.636%	$238.262	$238.26	$238.25	$238.30
Purchase #7	$65.35	9.163%	$71.338	$71.34	$71.35	$71.30
7 purchase totals =	$913.10		$973.0896	$973.09	$973.05	$973.10