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	$33.72	13.595%	$38.3042	$38.30	$38.30	$38.30
Purchase #2	$194.29	9.161%	$212.0889	$212.09	$212.10	$212.10
Purchase #3	$6.76	9.312%	$7.3895	$7.39	$7.40	$7.40
Purchase #4	$209.66	6.301%	$222.8707	$222.87	$222.85	$222.90
Purchase #5	$216.46	10.815%	$239.8701	$239.87	$239.85	$239.90
Purchase #6	$238.87	4.326%	$249.2035	$249.20	$249.20	$249.20
Purchase #7	$38.42	10.118%	$42.3073	$42.31	$42.30	$42.30
7 purchase totals =	$938.18		$1,012.0342	$1,012.03	$1,012.00	$1,012.10