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	$91.40	5.471%	$96.4005	$96.40	$96.40	$96.40
Purchase #2	$126.80	8.312%	$137.3396	$137.34	$137.35	$137.30
Purchase #3	$6.74	12.142%	$7.5584	$7.56	$7.55	$7.60
Purchase #4	$103.54	7.207%	$111.0021	$111.00	$111.00	$111.00
Purchase #5	$90.65	13.836%	$103.1923	$103.19	$103.20	$103.20
Purchase #6	$124.84	7.610%	$134.3403	$134.34	$134.35	$134.30
Purchase #7	$239.64	11.373%	$266.8943	$266.89	$266.90	$266.90
7 purchase totals =	$783.61		$856.7275	$856.72	$856.75	$856.70