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	$65.35	10.455%	$72.1823	$72.18	$72.20	$72.20
Purchase #2	$38.49	11.262%	$42.8247	$42.82	$42.80	$42.80
Purchase #3	$233.32	13.836%	$265.6022	$265.60	$265.60	$265.60
Purchase #4	$223.48	7.697%	$240.6813	$240.68	$240.70	$240.70
Purchase #5	$226.88	7.280%	$243.3969	$243.40	$243.40	$243.40
Purchase #6	$29.72	5.388%	$31.3213	$31.32	$31.30	$31.30
Purchase #7	$203.43	4.679%	$212.9485	$212.95	$212.95	$212.90
7 purchase totals =	$1,020.67		$1,108.9572	$1,108.95	$1,108.95	$1,108.90