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	$185.77	7.871%	$200.392	$200.39	$200.40	$200.40
Purchase #2	$98.66	10.120%	$108.6444	$108.64	$108.65	$108.60
Purchase #3	$79.77	3.399%	$82.4814	$82.48	$82.50	$82.50
Purchase #4	$55.41	7.286%	$59.4472	$59.45	$59.45	$59.40
Purchase #5	$30.48	10.541%	$33.6929	$33.69	$33.70	$33.70
Purchase #6	$248.51	12.697%	$280.0633	$280.06	$280.05	$280.10
Purchase #7	$162.28	6.337%	$172.5637	$172.56	$172.55	$172.60
7 purchase totals =	$860.88		$937.2849	$937.27	$937.30	$937.30