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	$71.97	9.152%	$78.5567	$78.56	$78.55	$78.60
Purchase #2	$235.28	7.792%	$253.613	$253.61	$253.60	$253.60
Purchase #3	$87.38	10.704%	$96.7332	$96.73	$96.75	$96.70
Purchase #4	$64.54	7.678%	$69.4954	$69.50	$69.50	$69.50
Purchase #5	$150.76	3.804%	$156.4949	$156.49	$156.50	$156.50
Purchase #6	$126.87	3.365%	$131.1392	$131.14	$131.15	$131.10
Purchase #7	$103.59	5.874%	$109.6749	$109.67	$109.65	$109.70
7 purchase totals =	$840.39		$895.7073	$895.70	$895.70	$895.70