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	$43.70	4.581%	$45.7019	$45.70	$45.70	$45.70
Purchase #2	$66.79	10.657%	$73.9078	$73.91	$73.90	$73.90
Purchase #3	$34.27	13.155%	$38.7782	$38.78	$38.80	$38.80
Purchase #4	$12.65	10.160%	$13.9352	$13.94	$13.95	$13.90
Purchase #5	$31.72	5.168%	$33.3593	$33.36	$33.35	$33.40
Purchase #6	$92.45	4.287%	$96.4133	$96.41	$96.40	$96.40
Purchase #7	$102.25	12.844%	$115.383	$115.38	$115.40	$115.40
7 purchase totals =	$383.83		$417.4787	$417.48	$417.50	$417.50