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	$36.82	12.588%	$41.4549	$41.45	$41.45	$41.50
Purchase #2	$185.69	6.643%	$198.0254	$198.03	$198.05	$198.00
Purchase #3	$94.80	5.251%	$99.7779	$99.78	$99.80	$99.80
Purchase #4	$244.54	10.109%	$269.2605	$269.26	$269.25	$269.30
Purchase #5	$181.46	4.788%	$190.1483	$190.15	$190.15	$190.10
Purchase #6	$211.57	3.299%	$218.5497	$218.55	$218.55	$218.50
Purchase #7	$171.38	7.556%	$184.3295	$184.33	$184.35	$184.30
7 purchase totals =	$1,126.26		$1,201.5462	$1,201.55	$1,201.60	$1,201.50