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	$57.82	13.280%	$65.4985	$65.50	$65.50	$65.50
Purchase #2	$117.92	7.360%	$126.5989	$126.60	$126.60	$126.60
Purchase #3	$162.43	13.479%	$184.3239	$184.32	$184.30	$184.30
Purchase #4	$241.95	13.330%	$274.2019	$274.20	$274.20	$274.20
Purchase #5	$77.95	6.179%	$82.7665	$82.77	$82.75	$82.80
Purchase #6	$92.51	11.594%	$103.2356	$103.24	$103.25	$103.20
Purchase #7	$199.64	9.365%	$218.3363	$218.34	$218.35	$218.30
7 purchase totals =	$950.22		$1,054.9616	$1,054.97	$1,054.95	$1,054.90