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	$152.59	8.164%	$165.0474	$165.05	$165.05	$165.00
Purchase #2	$143.63	13.450%	$162.9482	$162.95	$162.95	$162.90
Purchase #3	$33.32	8.644%	$36.2002	$36.20	$36.20	$36.20
Purchase #4	$158.30	5.540%	$167.0698	$167.07	$167.05	$167.10
Purchase #5	$181.38	3.563%	$187.8426	$187.84	$187.85	$187.80
Purchase #6	$126.77	3.816%	$131.6075	$131.61	$131.60	$131.60
Purchase #7	$148.30	12.752%	$167.2112	$167.21	$167.20	$167.20
7 purchase totals =	$944.29		$1,017.9269	$1,017.93	$1,017.90	$1,017.80