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	$190.61	13.253%	$215.8715	$215.87	$215.85	$215.90
Purchase #2	$13.39	7.432%	$14.3851	$14.39	$14.40	$14.40
Purchase #3	$18.98	11.388%	$21.1414	$21.14	$21.15	$21.10
Purchase #4	$123.65	3.491%	$127.9666	$127.97	$127.95	$128.00
Purchase #5	$91.76	4.127%	$95.5469	$95.55	$95.55	$95.50
Purchase #6	$183.66	7.860%	$198.0957	$198.10	$198.10	$198.10
Purchase #7	$201.95	13.345%	$228.9002	$228.90	$228.90	$228.90
7 purchase totals =	$824.00		$901.9074	$901.92	$901.90	$901.90