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	$43.79	5.613%	$46.2479	$46.25	$46.25	$46.20
Purchase #2	$147.83	10.511%	$163.3684	$163.37	$163.35	$163.40
Purchase #3	$166.89	8.135%	$180.4665	$180.47	$180.45	$180.50
Purchase #4	$92.38	4.317%	$96.368	$96.37	$96.35	$96.40
Purchase #5	$222.94	7.466%	$239.5847	$239.58	$239.60	$239.60
Purchase #6	$172.86	12.539%	$194.5349	$194.53	$194.55	$194.50
Purchase #7	$88.94	11.604%	$99.2606	$99.26	$99.25	$99.30
7 purchase totals =	$935.63		$1,019.8310	$1,019.83	$1,019.80	$1,019.90