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	$172.81	3.604%	$179.0381	$179.04	$179.05	$179.00
Purchase #2	$114.34	11.487%	$127.4742	$127.47	$127.45	$127.50
Purchase #3	$123.30	6.765%	$131.6412	$131.64	$131.65	$131.60
Purchase #4	$109.93	3.217%	$113.4664	$113.47	$113.45	$113.50
Purchase #5	$125.43	13.508%	$142.3731	$142.37	$142.35	$142.40
Purchase #6	$163.91	4.168%	$170.7418	$170.74	$170.75	$170.70
Purchase #7	$162.36	13.318%	$183.9831	$183.98	$184.00	$184.00
7 purchase totals =	$972.08		$1,048.7179	$1,048.71	$1,048.70	$1,048.70