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	$113.94	8.427%	$123.5417	$123.54	$123.55	$123.50
Purchase #2	$97.77	3.264%	$100.9612	$100.96	$100.95	$101.00
Purchase #3	$73.90	12.178%	$82.8995	$82.90	$82.90	$82.90
Purchase #4	$88.76	7.442%	$95.3655	$95.37	$95.35	$95.40
Purchase #5	$198.99	9.588%	$218.0692	$218.07	$218.05	$218.10
Purchase #6	$85.97	6.479%	$91.54	$91.54	$91.55	$91.50
Purchase #7	$154.28	13.515%	$175.1309	$175.13	$175.15	$175.10
7 purchase totals =	$813.61		$887.5080	$887.51	$887.50	$887.50