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	$195.47	7.613%	$210.3511	$210.35	$210.35	$210.40
Purchase #2	$56.81	7.625%	$61.1418	$61.14	$61.15	$61.10
Purchase #3	$241.57	12.470%	$271.6938	$271.69	$271.70	$271.70
Purchase #4	$137.47	5.369%	$144.8508	$144.85	$144.85	$144.90
Purchase #5	$104.68	4.617%	$109.5131	$109.51	$109.50	$109.50
Purchase #6	$77.64	9.725%	$85.1905	$85.19	$85.20	$85.20
Purchase #7	$116.58	12.232%	$130.8401	$130.84	$130.85	$130.80
7 purchase totals =	$930.22		$1,013.5812	$1,013.57	$1,013.60	$1,013.60