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	$33.64	13.116%	$38.0522	$38.05	$38.05	$38.10
Purchase #2	$216.82	13.423%	$245.9237	$245.92	$245.90	$245.90
Purchase #3	$56.59	5.583%	$59.7494	$59.75	$59.75	$59.70
Purchase #4	$51.59	12.672%	$58.1275	$58.13	$58.15	$58.10
Purchase #5	$63.28	12.685%	$71.3071	$71.31	$71.30	$71.30
Purchase #6	$238.77	10.691%	$264.2969	$264.30	$264.30	$264.30
Purchase #7	$43.41	13.477%	$49.2604	$49.26	$49.25	$49.30
7 purchase totals =	$704.10		$786.7172	$786.72	$786.70	$786.70