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	$221.87	5.241%	$233.4982	$233.50	$233.50	$233.50
Purchase #2	$184.53	13.409%	$209.2736	$209.27	$209.25	$209.30
Purchase #3	$148.62	4.554%	$155.3882	$155.39	$155.40	$155.40
Purchase #4	$31.88	10.811%	$35.3265	$35.33	$35.35	$35.30
Purchase #5	$196.87	12.495%	$221.4689	$221.47	$221.45	$221.50
Purchase #6	$92.74	11.873%	$103.751	$103.75	$103.75	$103.80
Purchase #7	$16.82	3.747%	$17.4502	$17.45	$17.45	$17.50
7 purchase totals =	$893.33		$976.1566	$976.16	$976.15	$976.30