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	$49.46	4.254%	$51.564	$51.56	$51.55	$51.60
Purchase #2	$184.53	5.350%	$194.4024	$194.40	$194.40	$194.40
Purchase #3	$40.76	6.671%	$43.4791	$43.48	$43.50	$43.50
Purchase #4	$194.82	3.301%	$201.251	$201.25	$201.25	$201.30
Purchase #5	$41.58	8.584%	$45.1492	$45.15	$45.15	$45.10
Purchase #6	$169.49	11.141%	$188.3729	$188.37	$188.35	$188.40
Purchase #7	$54.77	13.492%	$62.1596	$62.16	$62.15	$62.20
7 purchase totals =	$735.41		$786.3782	$786.37	$786.35	$786.50