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	$224.86	7.774%	$242.3406	$242.34	$242.35	$242.30
Purchase #2	$147.77	9.795%	$162.2441	$162.24	$162.25	$162.20
Purchase #3	$245.42	5.355%	$258.5622	$258.56	$258.55	$258.60
Purchase #4	$232.35	4.836%	$243.5864	$243.59	$243.60	$243.60
Purchase #5	$177.28	3.174%	$182.9069	$182.91	$182.90	$182.90
Purchase #6	$152.31	9.726%	$167.1237	$167.12	$167.10	$167.10
Purchase #7	$45.30	13.211%	$51.2846	$51.28	$51.30	$51.30
7 purchase totals =	$1,225.29		$1,308.0485	$1,308.04	$1,308.05	$1,308.00