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	$250.74	10.258%	$276.4609	$276.46	$276.45	$276.50
Purchase #2	$67.52	3.809%	$70.0918	$70.09	$70.10	$70.10
Purchase #3	$73.30	12.341%	$82.346	$82.35	$82.35	$82.30
Purchase #4	$246.87	8.447%	$267.7231	$267.72	$267.70	$267.70
Purchase #5	$82.87	8.528%	$89.9372	$89.94	$89.95	$89.90
Purchase #6	$174.38	6.622%	$185.9274	$185.93	$185.95	$185.90
Purchase #7	$55.92	7.865%	$60.3181	$60.32	$60.30	$60.30
7 purchase totals =	$951.60		$1,032.8045	$1,032.81	$1,032.80	$1,032.70