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	$46.53	5.221%	$48.9593	$48.96	$48.95	$49.00
Purchase #2	$201.93	4.798%	$211.6186	$211.62	$211.60	$211.60
Purchase #3	$38.98	9.205%	$42.5681	$42.57	$42.55	$42.60
Purchase #4	$104.45	3.740%	$108.3564	$108.36	$108.35	$108.40
Purchase #5	$86.29	3.874%	$89.6329	$89.63	$89.65	$89.60
Purchase #6	$166.38	3.810%	$172.7191	$172.72	$172.70	$172.70
Purchase #7	$46.59	9.545%	$51.037	$51.04	$51.05	$51.00
7 purchase totals =	$691.15		$724.8914	$724.90	$724.85	$724.90