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	$147.29	7.646%	$158.5518	$158.55	$158.55	$158.60
Purchase #2	$139.63	13.387%	$158.3223	$158.32	$158.30	$158.30
Purchase #3	$158.90	10.579%	$175.71	$175.71	$175.70	$175.70
Purchase #4	$186.62	4.324%	$194.6894	$194.69	$194.70	$194.70
Purchase #5	$233.62	12.185%	$262.0866	$262.09	$262.10	$262.10
Purchase #6	$188.82	8.366%	$204.6167	$204.62	$204.60	$204.60
Purchase #7	$37.56	13.403%	$42.5942	$42.59	$42.60	$42.60
7 purchase totals =	$1,092.44		$1,196.5710	$1,196.57	$1,196.55	$1,196.60