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	$48.90	10.218%	$53.8966	$53.90	$53.90	$53.90
Purchase #2	$31.66	5.825%	$33.5042	$33.50	$33.50	$33.50
Purchase #3	$174.65	6.157%	$185.4032	$185.40	$185.40	$185.40
Purchase #4	$130.35	7.358%	$139.9412	$139.94	$139.95	$139.90
Purchase #5	$190.45	13.826%	$216.7816	$216.78	$216.80	$216.80
Purchase #6	$118.86	12.355%	$133.5452	$133.55	$133.55	$133.50
Purchase #7	$225.57	10.679%	$249.6586	$249.66	$249.65	$249.70
7 purchase totals =	$920.44		$1,012.7306	$1,012.73	$1,012.75	$1,012.70