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	$144.58	12.273%	$162.3243	$162.32	$162.30	$162.30
Purchase #2	$189.90	10.830%	$210.4662	$210.47	$210.45	$210.50
Purchase #3	$226.72	9.786%	$248.9068	$248.91	$248.90	$248.90
Purchase #4	$146.74	6.687%	$156.5525	$156.55	$156.55	$156.60
Purchase #5	$28.96	4.639%	$30.3035	$30.30	$30.30	$30.30
Purchase #6	$35.87	12.711%	$40.4294	$40.43	$40.45	$40.40
Purchase #7	$207.86	12.851%	$234.5721	$234.57	$234.55	$234.60
7 purchase totals =	$980.63		$1,083.5548	$1,083.55	$1,083.50	$1,083.60