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	$200.91	5.697%	$212.3558	$212.36	$212.35	$212.40
Purchase #2	$79.73	3.376%	$82.4217	$82.42	$82.40	$82.40
Purchase #3	$241.69	6.369%	$257.0832	$257.08	$257.10	$257.10
Purchase #4	$67.48	10.140%	$74.3225	$74.32	$74.30	$74.30
Purchase #5	$160.44	3.110%	$165.4297	$165.43	$165.45	$165.40
Purchase #6	$115.80	12.741%	$130.5541	$130.55	$130.55	$130.60
Purchase #7	$90.30	4.262%	$94.1486	$94.15	$94.15	$94.10
7 purchase totals =	$956.35		$1,016.3156	$1,016.31	$1,016.30	$1,016.30