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	$102.63	8.436%	$111.2879	$111.29	$111.30	$111.30
Purchase #2	$174.72	12.468%	$196.5041	$196.50	$196.50	$196.50
Purchase #3	$67.78	11.357%	$75.4778	$75.48	$75.50	$75.50
Purchase #4	$217.29	13.116%	$245.7898	$245.79	$245.80	$245.80
Purchase #5	$121.77	10.572%	$134.6435	$134.64	$134.65	$134.60
Purchase #6	$194.74	10.536%	$215.2578	$215.26	$215.25	$215.30
Purchase #7	$107.62	10.847%	$119.2935	$119.29	$119.30	$119.30
7 purchase totals =	$986.55		$1,098.2544	$1,098.25	$1,098.30	$1,098.30