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	$78.75	9.722%	$86.4061	$86.41	$86.40	$86.40
Purchase #2	$169.65	12.303%	$190.522	$190.52	$190.50	$190.50
Purchase #3	$194.92	6.542%	$207.6717	$207.67	$207.65	$207.70
Purchase #4	$199.86	10.491%	$220.8273	$220.83	$220.85	$220.80
Purchase #5	$180.27	9.194%	$196.844	$196.84	$196.85	$196.80
Purchase #6	$142.54	5.592%	$150.5108	$150.51	$150.50	$150.50
Purchase #7	$54.77	5.718%	$57.9017	$57.90	$57.90	$57.90
7 purchase totals =	$1,020.76		$1,110.6836	$1,110.68	$1,110.65	$1,110.60