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	$181.44	8.462%	$196.7935	$196.79	$196.80	$196.80
Purchase #2	$207.32	3.821%	$215.2417	$215.24	$215.25	$215.20
Purchase #3	$136.66	13.103%	$154.5666	$154.57	$154.55	$154.60
Purchase #4	$112.43	13.662%	$127.7902	$127.79	$127.80	$127.80
Purchase #5	$222.57	5.460%	$234.7223	$234.72	$234.70	$234.70
Purchase #6	$89.28	8.186%	$96.5885	$96.59	$96.60	$96.60
Purchase #7	$81.28	8.556%	$88.2343	$88.23	$88.25	$88.20
7 purchase totals =	$1,030.98		$1,113.9371	$1,113.93	$1,113.95	$1,113.90