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	$118.92	5.366%	$125.3012	$125.30	$125.30	$125.30
Purchase #2	$245.71	11.630%	$274.2861	$274.29	$274.30	$274.30
Purchase #3	$94.90	9.167%	$103.5995	$103.60	$103.60	$103.60
Purchase #4	$54.43	9.787%	$59.7571	$59.76	$59.75	$59.80
Purchase #5	$240.36	7.575%	$258.5673	$258.57	$258.55	$258.60
Purchase #6	$138.38	11.504%	$154.2992	$154.30	$154.30	$154.30
Purchase #7	$70.65	10.172%	$77.8365	$77.84	$77.85	$77.80
7 purchase totals =	$963.35		$1,053.6469	$1,053.66	$1,053.65	$1,053.70