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	$147.83	10.106%	$162.7697	$162.77	$162.75	$162.80
Purchase #2	$154.93	4.809%	$162.3806	$162.38	$162.40	$162.40
Purchase #3	$48.69	9.502%	$53.3165	$53.32	$53.30	$53.30
Purchase #4	$83.31	13.547%	$94.596	$94.60	$94.60	$94.60
Purchase #5	$86.52	6.264%	$91.9396	$91.94	$91.95	$91.90
Purchase #6	$229.46	12.352%	$257.8029	$257.80	$257.80	$257.80
Purchase #7	$13.83	6.188%	$14.6858	$14.69	$14.70	$14.70
7 purchase totals =	$764.57		$837.4911	$837.50	$837.50	$837.50