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	$211.55	13.488%	$240.0839	$240.08	$240.10	$240.10
Purchase #2	$27.88	12.718%	$31.4258	$31.43	$31.45	$31.40
Purchase #3	$143.43	3.360%	$148.2492	$148.25	$148.25	$148.20
Purchase #4	$81.52	10.336%	$89.9459	$89.95	$89.95	$89.90
Purchase #5	$78.50	4.411%	$81.9626	$81.96	$81.95	$82.00
Purchase #6	$57.51	5.463%	$60.6518	$60.65	$60.65	$60.70
Purchase #7	$49.79	6.459%	$53.0059	$53.01	$53.00	$53.00
7 purchase totals =	$650.18		$705.3251	$705.33	$705.35	$705.30