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	$105.55	5.801%	$111.673	$111.67	$111.65	$111.70
Purchase #2	$73.70	6.159%	$78.2392	$78.24	$78.25	$78.20
Purchase #3	$57.42	13.636%	$65.2498	$65.25	$65.25	$65.20
Purchase #4	$154.59	6.320%	$164.3601	$164.36	$164.35	$164.40
Purchase #5	$17.66	11.510%	$19.6927	$19.69	$19.70	$19.70
Purchase #6	$243.34	13.822%	$276.9745	$276.97	$276.95	$277.00
Purchase #7	$130.58	12.801%	$147.2955	$147.30	$147.30	$147.30
7 purchase totals =	$782.84		$863.4848	$863.48	$863.45	$863.50