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	$69.98	12.115%	$78.4581	$78.46	$78.45	$78.50
Purchase #2	$15.84	6.444%	$16.8607	$16.86	$16.85	$16.90
Purchase #3	$148.35	5.461%	$156.4514	$156.45	$156.45	$156.50
Purchase #4	$32.62	12.164%	$36.5879	$36.59	$36.60	$36.60
Purchase #5	$169.43	6.398%	$180.2701	$180.27	$180.25	$180.30
Purchase #6	$116.61	9.563%	$127.7614	$127.76	$127.75	$127.80
Purchase #7	$95.57	6.199%	$101.4944	$101.49	$101.50	$101.50
7 purchase totals =	$648.40		$697.8840	$697.88	$697.85	$698.10