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	$158.70	5.588%	$167.5682	$167.57	$167.55	$167.60
Purchase #2	$238.48	3.364%	$246.5025	$246.50	$246.50	$246.50
Purchase #3	$54.48	9.580%	$59.6992	$59.70	$59.70	$59.70
Purchase #4	$137.70	6.411%	$146.5279	$146.53	$146.55	$146.50
Purchase #5	$73.86	13.697%	$83.9766	$83.98	$84.00	$84.00
Purchase #6	$170.69	8.397%	$185.0228	$185.02	$185.00	$185.00
Purchase #7	$7.48	5.177%	$7.8672	$7.87	$7.85	$7.90
7 purchase totals =	$841.39		$897.1644	$897.17	$897.15	$897.20