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	$163.71	6.738%	$174.7408	$174.74	$174.75	$174.70
Purchase #2	$21.96	6.650%	$23.4203	$23.42	$23.40	$23.40
Purchase #3	$164.57	13.866%	$187.3893	$187.39	$187.40	$187.40
Purchase #4	$191.91	9.374%	$209.8996	$209.90	$209.90	$209.90
Purchase #5	$81.94	10.782%	$90.7748	$90.77	$90.75	$90.80
Purchase #6	$76.35	12.662%	$86.0174	$86.02	$86.00	$86.00
Purchase #7	$187.42	4.840%	$196.4911	$196.49	$196.50	$196.50
7 purchase totals =	$887.86		$968.7333	$968.73	$968.70	$968.70