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	$140.75	11.227%	$156.552	$156.55	$156.55	$156.60
Purchase #2	$189.31	3.771%	$196.4489	$196.45	$196.45	$196.40
Purchase #3	$212.93	3.851%	$221.1299	$221.13	$221.15	$221.10
Purchase #4	$168.39	3.648%	$174.5329	$174.53	$174.55	$174.50
Purchase #5	$250.56	11.852%	$280.2564	$280.26	$280.25	$280.30
Purchase #6	$249.98	10.514%	$276.2629	$276.26	$276.25	$276.30
Purchase #7	$77.53	3.770%	$80.4529	$80.45	$80.45	$80.50
7 purchase totals =	$1,289.45		$1,385.6359	$1,385.63	$1,385.65	$1,385.70