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	$128.27	10.478%	$141.7101	$141.71	$141.70	$141.70
Purchase #2	$78.62	4.589%	$82.2279	$82.23	$82.25	$82.20
Purchase #3	$179.35	9.412%	$196.2304	$196.23	$196.25	$196.20
Purchase #4	$56.73	12.560%	$63.8553	$63.86	$63.85	$63.90
Purchase #5	$203.48	12.298%	$228.504	$228.50	$228.50	$228.50
Purchase #6	$173.73	11.834%	$194.2892	$194.29	$194.30	$194.30
Purchase #7	$56.82	10.431%	$62.7469	$62.75	$62.75	$62.70
7 purchase totals =	$877.00		$969.5638	$969.57	$969.60	$969.50