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	$24.64	4.654%	$25.7867	$25.79	$25.80	$25.80
Purchase #2	$40.49	4.547%	$42.3311	$42.33	$42.35	$42.30
Purchase #3	$112.69	4.444%	$117.6979	$117.70	$117.70	$117.70
Purchase #4	$82.26	10.255%	$90.6958	$90.70	$90.70	$90.70
Purchase #5	$137.64	6.547%	$146.6513	$146.65	$146.65	$146.70
Purchase #6	$54.79	5.360%	$57.7267	$57.73	$57.75	$57.70
Purchase #7	$167.84	11.281%	$186.774	$186.77	$186.75	$186.80
7 purchase totals =	$620.35		$667.6635	$667.67	$667.70	$667.70