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	$142.97	11.555%	$159.4902	$159.49	$159.50	$159.50
Purchase #2	$158.38	10.518%	$175.0384	$175.04	$175.05	$175.00
Purchase #3	$42.85	13.818%	$48.771	$48.77	$48.75	$48.80
Purchase #4	$100.52	4.148%	$104.6896	$104.69	$104.70	$104.70
Purchase #5	$74.83	10.723%	$82.854	$82.85	$82.85	$82.90
Purchase #6	$11.42	10.260%	$12.5917	$12.59	$12.60	$12.60
Purchase #7	$174.36	11.787%	$194.9118	$194.91	$194.90	$194.90
7 purchase totals =	$705.33		$778.3467	$778.34	$778.35	$778.40