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	$191.38	4.358%	$199.7203	$199.72	$199.70	$199.70
Purchase #2	$113.38	12.781%	$127.8711	$127.87	$127.85	$127.90
Purchase #3	$26.27	8.839%	$28.592	$28.59	$28.60	$28.60
Purchase #4	$198.58	5.273%	$209.0511	$209.05	$209.05	$209.10
Purchase #5	$161.90	6.166%	$171.8828	$171.88	$171.90	$171.90
Purchase #6	$211.67	13.634%	$240.5291	$240.53	$240.55	$240.50
Purchase #7	$249.97	12.292%	$280.6963	$280.70	$280.70	$280.70
7 purchase totals =	$1,153.15		$1,258.3427	$1,258.34	$1,258.35	$1,258.40