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	$181.86	3.299%	$187.8596	$187.86	$187.85	$187.90
Purchase #2	$73.57	6.549%	$78.3881	$78.39	$78.40	$78.40
Purchase #3	$114.83	11.780%	$128.357	$128.36	$128.35	$128.40
Purchase #4	$17.29	9.246%	$18.8886	$18.89	$18.90	$18.90
Purchase #5	$152.35	7.149%	$163.2415	$163.24	$163.25	$163.20
Purchase #6	$53.48	12.839%	$60.3463	$60.35	$60.35	$60.30
Purchase #7	$120.27	13.402%	$136.3886	$136.39	$136.40	$136.40
7 purchase totals =	$713.65		$773.4697	$773.48	$773.50	$773.50