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	$159.71	10.521%	$176.5131	$176.51	$176.50	$176.50
Purchase #2	$189.35	5.709%	$200.16	$200.16	$200.15	$200.20
Purchase #3	$247.31	7.279%	$265.3117	$265.31	$265.30	$265.30
Purchase #4	$120.36	9.220%	$131.4572	$131.46	$131.45	$131.50
Purchase #5	$113.75	12.293%	$127.7333	$127.73	$127.75	$127.70
Purchase #6	$108.77	8.734%	$118.27	$118.27	$118.25	$118.30
Purchase #7	$88.68	4.300%	$92.4932	$92.49	$92.50	$92.50
7 purchase totals =	$1,027.93		$1,111.9385	$1,111.93	$1,111.90	$1,112.00