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	$226.46	9.681%	$248.3836	$248.38	$248.40	$248.40
Purchase #2	$217.73	9.437%	$238.2772	$238.28	$238.30	$238.30
Purchase #3	$99.53	10.411%	$109.8921	$109.89	$109.90	$109.90
Purchase #4	$185.28	12.542%	$208.5178	$208.52	$208.50	$208.50
Purchase #5	$189.80	3.587%	$196.6081	$196.61	$196.60	$196.60
Purchase #6	$29.74	3.813%	$30.874	$30.87	$30.85	$30.90
Purchase #7	$155.51	10.662%	$172.0905	$172.09	$172.10	$172.10
7 purchase totals =	$1,104.05		$1,204.6433	$1,204.64	$1,204.65	$1,204.70