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	$89.66	12.613%	$100.9688	$100.97	$100.95	$101.00
Purchase #2	$130.75	13.252%	$148.077	$148.08	$148.10	$148.10
Purchase #3	$139.79	13.702%	$158.944	$158.94	$158.95	$158.90
Purchase #4	$220.90	13.761%	$251.298	$251.30	$251.30	$251.30
Purchase #5	$38.30	12.319%	$43.0182	$43.02	$43.00	$43.00
Purchase #6	$163.85	9.816%	$179.9335	$179.93	$179.95	$179.90
Purchase #7	$194.78	7.364%	$209.1236	$209.12	$209.10	$209.10
7 purchase totals =	$978.03		$1,091.3631	$1,091.36	$1,091.35	$1,091.30