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	$49.91	9.708%	$54.7553	$54.76	$54.75	$54.80
Purchase #2	$103.64	3.223%	$106.9803	$106.98	$107.00	$107.00
Purchase #3	$8.83	5.777%	$9.3401	$9.34	$9.35	$9.30
Purchase #4	$95.67	5.379%	$100.8161	$100.82	$100.80	$100.80
Purchase #5	$73.84	11.257%	$82.1522	$82.15	$82.15	$82.20
Purchase #6	$60.32	6.867%	$64.4622	$64.46	$64.45	$64.50
Purchase #7	$99.91	3.722%	$103.6287	$103.63	$103.65	$103.60
7 purchase totals =	$492.12		$522.1349	$522.14	$522.15	$522.20