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	$142.42	8.751%	$154.8832	$154.88	$154.90	$154.90
Purchase #2	$29.62	9.277%	$32.3678	$32.37	$32.35	$32.40
Purchase #3	$78.59	5.421%	$82.8504	$82.85	$82.85	$82.90
Purchase #4	$179.32	10.488%	$198.1271	$198.13	$198.15	$198.10
Purchase #5	$236.32	4.232%	$246.3211	$246.32	$246.30	$246.30
Purchase #6	$89.48	9.459%	$97.9439	$97.94	$97.95	$97.90
Purchase #7	$110.72	11.756%	$123.7362	$123.74	$123.75	$123.70
7 purchase totals =	$866.47		$936.2297	$936.23	$936.25	$936.20