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	$53.59	3.520%	$55.4764	$55.48	$55.50	$55.50
Purchase #2	$50.86	6.131%	$53.9782	$53.98	$54.00	$54.00
Purchase #3	$103.90	6.126%	$110.2649	$110.26	$110.25	$110.30
Purchase #4	$122.56	4.146%	$127.6413	$127.64	$127.65	$127.60
Purchase #5	$112.99	11.726%	$126.2392	$126.24	$126.25	$126.20
Purchase #6	$84.89	13.618%	$96.4503	$96.45	$96.45	$96.50
Purchase #7	$200.67	12.538%	$225.83	$225.83	$225.85	$225.80
7 purchase totals =	$729.46		$795.8803	$795.88	$795.95	$795.90