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	$61.48	9.404%	$67.2616	$67.26	$67.25	$67.30
Purchase #2	$227.99	4.701%	$238.7078	$238.71	$238.70	$238.70
Purchase #3	$39.26	7.225%	$42.0965	$42.10	$42.10	$42.10
Purchase #4	$53.63	8.311%	$58.0872	$58.09	$58.10	$58.10
Purchase #5	$32.27	3.845%	$33.5108	$33.51	$33.50	$33.50
Purchase #6	$200.48	10.495%	$221.5204	$221.52	$221.50	$221.50
Purchase #7	$248.28	8.791%	$270.1063	$270.11	$270.10	$270.10
7 purchase totals =	$863.39		$931.2906	$931.30	$931.25	$931.30