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	$60.34	13.830%	$68.685	$68.69	$68.70	$68.70
Purchase #2	$97.74	5.654%	$103.2662	$103.27	$103.25	$103.30
Purchase #3	$93.86	12.432%	$105.5287	$105.53	$105.55	$105.50
Purchase #4	$240.61	12.576%	$270.8691	$270.87	$270.85	$270.90
Purchase #5	$153.73	11.653%	$171.6442	$171.64	$171.65	$171.60
Purchase #6	$197.26	9.779%	$216.5501	$216.55	$216.55	$216.60
Purchase #7	$81.89	10.625%	$90.5908	$90.59	$90.60	$90.60
7 purchase totals =	$925.43		$1,027.1341	$1,027.14	$1,027.15	$1,027.20