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	$114.30	4.352%	$119.2743	$119.27	$119.25	$119.30
Purchase #2	$178.52	11.364%	$198.807	$198.81	$198.80	$198.80
Purchase #3	$176.66	8.653%	$191.9464	$191.95	$191.95	$191.90
Purchase #4	$185.69	7.447%	$199.5183	$199.52	$199.50	$199.50
Purchase #5	$177.32	3.559%	$183.6308	$183.63	$183.65	$183.60
Purchase #6	$131.25	8.831%	$142.8407	$142.84	$142.85	$142.80
Purchase #7	$66.90	9.650%	$73.3559	$73.36	$73.35	$73.40
7 purchase totals =	$1,030.64		$1,109.3734	$1,109.38	$1,109.35	$1,109.30