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	$80.44	7.399%	$86.3918	$86.39	$86.40	$86.40
Purchase #2	$168.45	9.829%	$185.007	$185.01	$185.00	$185.00
Purchase #3	$13.39	10.285%	$14.7672	$14.77	$14.75	$14.80
Purchase #4	$152.59	3.514%	$157.952	$157.95	$157.95	$158.00
Purchase #5	$135.66	6.302%	$144.2093	$144.21	$144.20	$144.20
Purchase #6	$221.34	12.299%	$248.5626	$248.56	$248.55	$248.60
Purchase #7	$95.80	10.133%	$105.5074	$105.51	$105.50	$105.50
7 purchase totals =	$867.67		$942.3973	$942.40	$942.35	$942.50