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	$243.53	6.169%	$258.5534	$258.55	$258.55	$258.60
Purchase #2	$104.36	12.725%	$117.6398	$117.64	$117.65	$117.60
Purchase #3	$159.42	7.651%	$171.6172	$171.62	$171.60	$171.60
Purchase #4	$174.35	9.207%	$190.4024	$190.40	$190.40	$190.40
Purchase #5	$203.31	13.657%	$231.076	$231.08	$231.10	$231.10
Purchase #6	$100.85	4.521%	$105.4094	$105.41	$105.40	$105.40
Purchase #7	$27.59	7.290%	$29.6013	$29.60	$29.60	$29.60
7 purchase totals =	$1,013.41		$1,104.2995	$1,104.30	$1,104.30	$1,104.30