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	$40.78	6.701%	$43.5127	$43.51	$43.50	$43.50
Purchase #2	$94.39	11.187%	$104.9494	$104.95	$104.95	$104.90
Purchase #3	$193.39	5.259%	$203.5604	$203.56	$203.55	$203.60
Purchase #4	$240.90	5.804%	$254.8818	$254.88	$254.90	$254.90
Purchase #5	$161.86	3.505%	$167.5332	$167.53	$167.55	$167.50
Purchase #6	$104.43	6.636%	$111.36	$111.36	$111.35	$111.40
Purchase #7	$219.43	3.831%	$227.8364	$227.84	$227.85	$227.80
7 purchase totals =	$1,055.18		$1,113.6339	$1,113.63	$1,113.65	$1,113.60