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	$231.82	9.455%	$253.7386	$253.74	$253.75	$253.70
Purchase #2	$79.85	10.277%	$88.0562	$88.06	$88.05	$88.10
Purchase #3	$163.91	5.457%	$172.8546	$172.85	$172.85	$172.90
Purchase #4	$99.80	9.443%	$109.2241	$109.22	$109.20	$109.20
Purchase #5	$189.92	6.663%	$202.5744	$202.57	$202.55	$202.60
Purchase #6	$118.82	10.537%	$131.3401	$131.34	$131.35	$131.30
Purchase #7	$99.95	8.610%	$108.5557	$108.56	$108.55	$108.60
7 purchase totals =	$984.07		$1,066.3437	$1,066.34	$1,066.30	$1,066.40