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	$229.58	5.138%	$241.3758	$241.38	$241.40	$241.40
Purchase #2	$198.59	7.651%	$213.7841	$213.78	$213.80	$213.80
Purchase #3	$216.97	6.671%	$231.4441	$231.44	$231.45	$231.40
Purchase #4	$213.42	3.830%	$221.594	$221.59	$221.60	$221.60
Purchase #5	$185.38	6.187%	$196.8495	$196.85	$196.85	$196.80
Purchase #6	$10.92	5.436%	$11.5136	$11.51	$11.50	$11.50
Purchase #7	$238.47	10.382%	$263.228	$263.23	$263.25	$263.20
7 purchase totals =	$1,293.33		$1,379.7891	$1,379.78	$1,379.85	$1,379.70