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	$233.38	9.611%	$255.8102	$255.81	$255.80	$255.80
Purchase #2	$59.83	3.578%	$61.9707	$61.97	$61.95	$62.00
Purchase #3	$129.52	10.271%	$142.823	$142.82	$142.80	$142.80
Purchase #4	$124.98	4.783%	$130.9578	$130.96	$130.95	$131.00
Purchase #5	$146.83	6.104%	$155.7925	$155.79	$155.80	$155.80
Purchase #6	$71.35	9.486%	$78.1183	$78.12	$78.10	$78.10
Purchase #7	$80.28	10.170%	$88.4445	$88.44	$88.45	$88.40
7 purchase totals =	$846.17		$913.9170	$913.91	$913.85	$913.90