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	$65.90	7.525%	$70.859	$70.86	$70.85	$70.90
Purchase #2	$47.83	9.851%	$52.5417	$52.54	$52.55	$52.50
Purchase #3	$222.87	12.347%	$250.3878	$250.39	$250.40	$250.40
Purchase #4	$194.98	6.782%	$208.2035	$208.20	$208.20	$208.20
Purchase #5	$148.72	12.556%	$167.3933	$167.39	$167.40	$167.40
Purchase #6	$184.37	5.551%	$194.6044	$194.60	$194.60	$194.60
Purchase #7	$93.90	4.751%	$98.3612	$98.36	$98.35	$98.40
7 purchase totals =	$958.57		$1,042.3509	$1,042.34	$1,042.35	$1,042.40