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	$55.89	9.112%	$60.9827	$60.98	$61.00	$61.00
Purchase #2	$25.73	10.601%	$28.4576	$28.46	$28.45	$28.50
Purchase #3	$25.87	4.466%	$27.0254	$27.03	$27.05	$27.00
Purchase #4	$141.30	3.565%	$146.3373	$146.34	$146.35	$146.30
Purchase #5	$237.55	5.490%	$250.5915	$250.59	$250.60	$250.60
Purchase #6	$186.43	10.146%	$205.3452	$205.35	$205.35	$205.30
Purchase #7	$21.51	13.382%	$24.3885	$24.39	$24.40	$24.40
7 purchase totals =	$694.28		$743.1282	$743.14	$743.20	$743.10