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	$116.34	13.304%	$131.8179	$131.82	$131.80	$131.80
Purchase #2	$172.37	4.738%	$180.5369	$180.54	$180.55	$180.50
Purchase #3	$134.45	6.204%	$142.7913	$142.79	$142.80	$142.80
Purchase #4	$237.92	11.286%	$264.7717	$264.77	$264.75	$264.80
Purchase #5	$29.70	13.660%	$33.757	$33.76	$33.75	$33.80
Purchase #6	$185.39	9.231%	$202.5034	$202.50	$202.50	$202.50
Purchase #7	$174.44	4.632%	$182.5201	$182.52	$182.50	$182.50
7 purchase totals =	$1,050.61		$1,138.6983	$1,138.70	$1,138.65	$1,138.70