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	$47.78	12.261%	$53.6383	$53.64	$53.65	$53.60
Purchase #2	$198.96	7.511%	$213.9039	$213.90	$213.90	$213.90
Purchase #3	$250.46	6.769%	$267.4136	$267.41	$267.40	$267.40
Purchase #4	$51.67	10.446%	$57.0674	$57.07	$57.05	$57.10
Purchase #5	$200.61	4.426%	$209.489	$209.49	$209.50	$209.50
Purchase #6	$91.60	7.635%	$98.5937	$98.59	$98.60	$98.60
Purchase #7	$146.34	12.470%	$164.5886	$164.59	$164.60	$164.60
7 purchase totals =	$987.42		$1,064.6945	$1,064.69	$1,064.70	$1,064.70