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	$240.97	11.491%	$268.6599	$268.66	$268.65	$268.70
Purchase #2	$38.55	13.388%	$43.7111	$43.71	$43.70	$43.70
Purchase #3	$100.69	5.136%	$105.8614	$105.86	$105.85	$105.90
Purchase #4	$216.93	8.635%	$235.6619	$235.66	$235.65	$235.70
Purchase #5	$56.55	10.127%	$62.2768	$62.28	$62.30	$62.30
Purchase #6	$162.87	5.336%	$171.5607	$171.56	$171.55	$171.60
Purchase #7	$203.89	13.519%	$231.4539	$231.45	$231.45	$231.50
7 purchase totals =	$1,020.45		$1,119.1857	$1,119.18	$1,119.15	$1,119.40