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	$154.28	10.826%	$170.9824	$170.98	$171.00	$171.00
Purchase #2	$74.56	11.323%	$83.0024	$83.00	$83.00	$83.00
Purchase #3	$38.99	11.550%	$43.4933	$43.49	$43.50	$43.50
Purchase #4	$80.40	6.412%	$85.5552	$85.56	$85.55	$85.60
Purchase #5	$60.43	11.113%	$67.1456	$67.15	$67.15	$67.10
Purchase #6	$147.56	9.159%	$161.075	$161.08	$161.10	$161.10
Purchase #7	$35.35	11.373%	$39.3704	$39.37	$39.35	$39.40
7 purchase totals =	$591.57		$650.6243	$650.63	$650.65	$650.70