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	$238.50	7.435%	$256.2325	$256.23	$256.25	$256.20
Purchase #2	$214.82	6.192%	$228.1217	$228.12	$228.10	$228.10
Purchase #3	$44.54	4.586%	$46.5826	$46.58	$46.60	$46.60
Purchase #4	$51.85	4.171%	$54.0127	$54.01	$54.00	$54.00
Purchase #5	$241.49	9.566%	$264.5909	$264.59	$264.60	$264.60
Purchase #6	$78.82	4.302%	$82.2108	$82.21	$82.20	$82.20
Purchase #7	$144.32	6.481%	$153.6734	$153.67	$153.65	$153.70
7 purchase totals =	$1,014.34		$1,085.4246	$1,085.41	$1,085.40	$1,085.40