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	$142.91	6.540%	$152.2563	$152.26	$152.25	$152.30
Purchase #2	$68.55	13.650%	$77.9071	$77.91	$77.90	$77.90
Purchase #3	$51.67	13.363%	$58.5747	$58.57	$58.55	$58.60
Purchase #4	$119.30	10.165%	$131.4268	$131.43	$131.45	$131.40
Purchase #5	$42.85	11.677%	$47.8536	$47.85	$47.85	$47.90
Purchase #6	$97.98	5.559%	$103.4267	$103.43	$103.45	$103.40
Purchase #7	$145.26	10.639%	$160.7142	$160.71	$160.70	$160.70
7 purchase totals =	$668.52		$732.1594	$732.16	$732.15	$732.20