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	$80.80	7.453%	$86.822	$86.82	$86.80	$86.80
Purchase #2	$147.72	3.412%	$152.7602	$152.76	$152.75	$152.80
Purchase #3	$107.95	4.427%	$112.7289	$112.73	$112.75	$112.70
Purchase #4	$116.82	3.182%	$120.5372	$120.54	$120.55	$120.50
Purchase #5	$16.88	12.205%	$18.9402	$18.94	$18.95	$18.90
Purchase #6	$246.48	7.116%	$264.0195	$264.02	$264.00	$264.00
Purchase #7	$148.69	10.819%	$164.7768	$164.78	$164.80	$164.80
7 purchase totals =	$865.34		$920.5848	$920.59	$920.60	$920.50