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	$73.36	4.670%	$76.7859	$76.79	$76.80	$76.80
Purchase #2	$205.54	8.614%	$223.2452	$223.25	$223.25	$223.20
Purchase #3	$31.48	5.422%	$33.1868	$33.19	$33.20	$33.20
Purchase #4	$138.70	8.574%	$150.5921	$150.59	$150.60	$150.60
Purchase #5	$158.90	3.419%	$164.3328	$164.33	$164.35	$164.30
Purchase #6	$66.53	7.314%	$71.396	$71.40	$71.40	$71.40
Purchase #7	$24.65	12.587%	$27.7527	$27.75	$27.75	$27.80
7 purchase totals =	$699.16		$747.2915	$747.30	$747.35	$747.30