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	$67.96	9.302%	$74.2816	$74.28	$74.30	$74.30
Purchase #2	$234.71	9.676%	$257.4205	$257.42	$257.40	$257.40
Purchase #3	$87.71	7.454%	$94.2479	$94.25	$94.25	$94.20
Purchase #4	$78.59	5.393%	$82.8284	$82.83	$82.85	$82.80
Purchase #5	$119.36	12.121%	$133.8276	$133.83	$133.85	$133.80
Purchase #6	$103.54	7.368%	$111.1688	$111.17	$111.15	$111.20
Purchase #7	$27.76	13.601%	$31.5356	$31.54	$31.55	$31.50
7 purchase totals =	$719.63		$785.3104	$785.32	$785.35	$785.20