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	$197.76	4.652%	$206.9598	$206.96	$206.95	$207.00
Purchase #2	$237.53	13.253%	$269.0099	$269.01	$269.00	$269.00
Purchase #3	$115.97	10.681%	$128.3568	$128.36	$128.35	$128.40
Purchase #4	$19.64	8.391%	$21.288	$21.29	$21.30	$21.30
Purchase #5	$18.45	13.144%	$20.8751	$20.88	$20.90	$20.90
Purchase #6	$107.46	3.862%	$111.6101	$111.61	$111.60	$111.60
Purchase #7	$164.91	12.132%	$184.9169	$184.92	$184.90	$184.90
7 purchase totals =	$861.72		$943.0166	$943.03	$943.00	$943.10