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	$100.96	5.436%	$106.4482	$106.45	$106.45	$106.40
Purchase #2	$30.72	10.744%	$34.0206	$34.02	$34.00	$34.00
Purchase #3	$33.51	10.417%	$37.0007	$37.00	$37.00	$37.00
Purchase #4	$72.82	11.585%	$81.2562	$81.26	$81.25	$81.30
Purchase #5	$74.77	12.158%	$83.8605	$83.86	$83.85	$83.90
Purchase #6	$208.71	7.155%	$223.6432	$223.64	$223.65	$223.60
Purchase #7	$78.85	13.751%	$89.6927	$89.69	$89.70	$89.70
7 purchase totals =	$600.34		$655.9221	$655.92	$655.90	$655.90