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	$105.45	7.657%	$113.5243	$113.52	$113.50	$113.50
Purchase #2	$97.49	11.814%	$109.0075	$109.01	$109.00	$109.00
Purchase #3	$51.49	4.591%	$53.8539	$53.85	$53.85	$53.90
Purchase #4	$155.65	4.408%	$162.5111	$162.51	$162.50	$162.50
Purchase #5	$244.65	7.375%	$262.6929	$262.69	$262.70	$262.70
Purchase #6	$58.97	3.514%	$61.0422	$61.04	$61.05	$61.00
Purchase #7	$173.45	9.354%	$189.6745	$189.67	$189.65	$189.70
7 purchase totals =	$887.15		$952.3064	$952.29	$952.25	$952.30