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	$57.30	11.570%	$63.9296	$63.93	$63.95	$63.90
Purchase #2	$79.27	5.280%	$83.4555	$83.46	$83.45	$83.50
Purchase #3	$206.26	8.557%	$223.9097	$223.91	$223.90	$223.90
Purchase #4	$177.82	6.192%	$188.8306	$188.83	$188.85	$188.80
Purchase #5	$77.81	9.275%	$85.0269	$85.03	$85.05	$85.00
Purchase #6	$69.45	4.683%	$72.7023	$72.70	$72.70	$72.70
Purchase #7	$172.59	9.739%	$189.3985	$189.40	$189.40	$189.40
7 purchase totals =	$840.50		$907.2531	$907.26	$907.30	$907.20