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	$225.32	5.419%	$237.5301	$237.53	$237.55	$237.50
Purchase #2	$87.25	12.168%	$97.8666	$97.87	$97.85	$97.90
Purchase #3	$55.75	3.709%	$57.8178	$57.82	$57.80	$57.80
Purchase #4	$73.59	4.825%	$77.1407	$77.14	$77.15	$77.10
Purchase #5	$150.36	9.498%	$164.6412	$164.64	$164.65	$164.60
Purchase #6	$105.35	5.803%	$111.4635	$111.46	$111.45	$111.50
Purchase #7	$127.47	9.307%	$139.3336	$139.33	$139.35	$139.30
7 purchase totals =	$825.09		$885.7935	$885.79	$885.80	$885.70