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	$52.69	8.473%	$57.1544	$57.15	$57.15	$57.20
Purchase #2	$22.59	12.629%	$25.4429	$25.44	$25.45	$25.40
Purchase #3	$77.97	5.583%	$82.3231	$82.32	$82.30	$82.30
Purchase #4	$67.65	7.553%	$72.7596	$72.76	$72.75	$72.80
Purchase #5	$55.39	13.484%	$62.8588	$62.86	$62.85	$62.90
Purchase #6	$6.77	12.822%	$7.638	$7.64	$7.65	$7.60
Purchase #7	$213.55	11.516%	$238.1424	$238.14	$238.15	$238.10
7 purchase totals =	$496.61		$546.3192	$546.31	$546.30	$546.30