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	$72.32	4.266%	$75.4052	$75.41	$75.40	$75.40
Purchase #2	$153.32	3.402%	$158.5359	$158.54	$158.55	$158.50
Purchase #3	$97.44	12.284%	$109.4095	$109.41	$109.40	$109.40
Purchase #4	$139.94	5.152%	$147.1497	$147.15	$147.15	$147.10
Purchase #5	$158.39	6.758%	$169.094	$169.09	$169.10	$169.10
Purchase #6	$229.59	8.497%	$249.0983	$249.10	$249.10	$249.10
Purchase #7	$171.37	4.376%	$178.8692	$178.87	$178.85	$178.90
7 purchase totals =	$1,022.37		$1,087.5618	$1,087.57	$1,087.55	$1,087.50