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	$36.97	10.276%	$40.769	$40.77	$40.75	$40.80
Purchase #2	$212.50	12.162%	$238.3443	$238.34	$238.35	$238.30
Purchase #3	$124.44	3.108%	$128.3076	$128.31	$128.30	$128.30
Purchase #4	$62.38	10.706%	$69.0584	$69.06	$69.05	$69.10
Purchase #5	$150.44	11.853%	$168.2717	$168.27	$168.25	$168.30
Purchase #6	$245.43	6.715%	$261.9106	$261.91	$261.90	$261.90
Purchase #7	$228.86	10.705%	$253.3595	$253.36	$253.35	$253.40
7 purchase totals =	$1,061.02		$1,160.0211	$1,160.02	$1,159.95	$1,160.10