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	$174.83	5.537%	$184.5103	$184.51	$184.50	$184.50
Purchase #2	$115.71	6.320%	$123.0229	$123.02	$123.00	$123.00
Purchase #3	$245.73	7.302%	$263.6732	$263.67	$263.65	$263.70
Purchase #4	$167.30	7.307%	$179.5246	$179.52	$179.50	$179.50
Purchase #5	$78.95	11.458%	$87.9961	$88.00	$88.00	$88.00
Purchase #6	$201.40	3.289%	$208.024	$208.02	$208.00	$208.00
Purchase #7	$37.59	8.622%	$40.831	$40.83	$40.85	$40.80
7 purchase totals =	$1,021.51		$1,087.5821	$1,087.57	$1,087.50	$1,087.50