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	$100.84	13.643%	$114.5976	$114.60	$114.60	$114.60
Purchase #2	$213.69	10.393%	$235.8988	$235.90	$235.90	$235.90
Purchase #3	$180.47	5.708%	$190.7712	$190.77	$190.75	$190.80
Purchase #4	$79.27	4.549%	$82.876	$82.88	$82.90	$82.90
Purchase #5	$142.36	12.713%	$160.4582	$160.46	$160.45	$160.50
Purchase #6	$170.62	11.123%	$189.5981	$189.60	$189.60	$189.60
Purchase #7	$113.86	12.219%	$127.7726	$127.77	$127.75	$127.80
7 purchase totals =	$1,001.11		$1,101.9725	$1,101.98	$1,101.95	$1,102.10