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	$110.54	4.566%	$115.5873	$115.59	$115.60	$115.60
Purchase #2	$249.46	3.756%	$258.8297	$258.83	$258.85	$258.80
Purchase #3	$89.50	11.674%	$99.9482	$99.95	$99.95	$99.90
Purchase #4	$229.83	12.630%	$258.8575	$258.86	$258.85	$258.90
Purchase #5	$41.41	11.420%	$46.139	$46.14	$46.15	$46.10
Purchase #6	$117.61	9.629%	$128.9347	$128.93	$128.95	$128.90
Purchase #7	$244.75	5.453%	$258.0962	$258.10	$258.10	$258.10
7 purchase totals =	$1,083.10		$1,166.3926	$1,166.40	$1,166.45	$1,166.30