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	$187.89	10.179%	$207.0153	$207.02	$207.00	$207.00
Purchase #2	$17.70	3.748%	$18.3634	$18.36	$18.35	$18.40
Purchase #3	$142.75	10.747%	$158.0913	$158.09	$158.10	$158.10
Purchase #4	$245.31	8.689%	$266.625	$266.63	$266.65	$266.60
Purchase #5	$119.94	7.414%	$128.8324	$128.83	$128.85	$128.80
Purchase #6	$94.90	3.170%	$97.9083	$97.91	$97.90	$97.90
Purchase #7	$229.37	11.225%	$255.1168	$255.12	$255.10	$255.10
7 purchase totals =	$1,037.86		$1,131.9525	$1,131.96	$1,131.95	$1,131.90