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	$47.86	7.750%	$51.5692	$51.57	$51.55	$51.60
Purchase #2	$192.32	13.816%	$218.8909	$218.89	$218.90	$218.90
Purchase #3	$236.79	5.401%	$249.579	$249.58	$249.60	$249.60
Purchase #4	$192.56	13.225%	$218.0261	$218.03	$218.05	$218.00
Purchase #5	$158.33	6.146%	$168.061	$168.06	$168.05	$168.10
Purchase #6	$44.59	12.362%	$50.1022	$50.10	$50.10	$50.10
Purchase #7	$187.61	4.529%	$196.1069	$196.11	$196.10	$196.10
7 purchase totals =	$1,060.06		$1,152.3353	$1,152.34	$1,152.35	$1,152.40