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	$140.85	10.541%	$155.697	$155.70	$155.70	$155.70
Purchase #2	$217.27	5.217%	$228.605	$228.61	$228.60	$228.60
Purchase #3	$210.98	5.689%	$222.9827	$222.98	$223.00	$223.00
Purchase #4	$111.78	13.837%	$127.247	$127.25	$127.25	$127.20
Purchase #5	$174.82	13.467%	$198.363	$198.36	$198.35	$198.40
Purchase #6	$84.52	7.102%	$90.5226	$90.52	$90.50	$90.50
Purchase #7	$240.56	10.125%	$264.9167	$264.92	$264.90	$264.90
7 purchase totals =	$1,180.78		$1,288.3340	$1,288.34	$1,288.30	$1,288.30