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	$74.25	11.432%	$82.7383	$82.74	$82.75	$82.70
Purchase #2	$39.30	3.710%	$40.758	$40.76	$40.75	$40.80
Purchase #3	$167.87	3.519%	$173.7773	$173.78	$173.80	$173.80
Purchase #4	$103.30	13.848%	$117.605	$117.61	$117.60	$117.60
Purchase #5	$140.52	11.604%	$156.8259	$156.83	$156.85	$156.80
Purchase #6	$214.75	13.180%	$243.0541	$243.05	$243.05	$243.10
Purchase #7	$166.25	8.319%	$180.0803	$180.08	$180.10	$180.10
7 purchase totals =	$906.24		$994.8389	$994.85	$994.90	$994.90