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	$235.45	10.190%	$259.4424	$259.44	$259.45	$259.40
Purchase #2	$152.45	4.614%	$159.484	$159.48	$159.50	$159.50
Purchase #3	$39.91	13.116%	$45.1446	$45.14	$45.15	$45.10
Purchase #4	$76.86	7.766%	$82.8289	$82.83	$82.85	$82.80
Purchase #5	$91.65	7.466%	$98.4926	$98.49	$98.50	$98.50
Purchase #6	$158.35	13.241%	$179.3171	$179.32	$179.30	$179.30
Purchase #7	$115.62	8.422%	$125.3575	$125.36	$125.35	$125.40
7 purchase totals =	$870.29		$950.0671	$950.06	$950.10	$950.00