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	$210.88	6.455%	$224.4923	$224.49	$224.50	$224.50
Purchase #2	$133.60	6.714%	$142.5699	$142.57	$142.55	$142.60
Purchase #3	$39.89	6.290%	$42.3991	$42.40	$42.40	$42.40
Purchase #4	$167.33	13.743%	$190.3262	$190.33	$190.35	$190.30
Purchase #5	$22.97	4.716%	$24.0533	$24.05	$24.05	$24.10
Purchase #6	$203.30	9.644%	$222.9063	$222.91	$222.90	$222.90
Purchase #7	$217.56	12.612%	$244.9987	$245.00	$245.00	$245.00
7 purchase totals =	$995.53		$1,091.7458	$1,091.75	$1,091.75	$1,091.80