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	$250.48	10.399%	$276.5274	$276.53	$276.55	$276.50
Purchase #2	$115.88	13.630%	$131.6744	$131.67	$131.65	$131.70
Purchase #3	$64.50	4.584%	$67.4567	$67.46	$67.45	$67.50
Purchase #4	$196.80	13.402%	$223.1751	$223.18	$223.20	$223.20
Purchase #5	$94.83	9.490%	$103.8294	$103.83	$103.85	$103.80
Purchase #6	$169.27	5.614%	$178.7728	$178.77	$178.75	$178.80
Purchase #7	$183.55	8.843%	$199.7813	$199.78	$199.80	$199.80
7 purchase totals =	$1,075.31		$1,181.2171	$1,181.22	$1,181.25	$1,181.30