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	$191.68	3.765%	$198.8968	$198.90	$198.90	$198.90
Purchase #2	$68.89	13.807%	$78.4016	$78.40	$78.40	$78.40
Purchase #3	$249.53	11.340%	$277.8267	$277.83	$277.85	$277.80
Purchase #4	$192.48	11.801%	$215.1946	$215.19	$215.20	$215.20
Purchase #5	$94.95	3.391%	$98.1698	$98.17	$98.15	$98.20
Purchase #6	$241.77	11.773%	$270.2336	$270.23	$270.25	$270.20
Purchase #7	$240.35	10.360%	$265.2503	$265.25	$265.25	$265.30
7 purchase totals =	$1,279.65		$1,403.9734	$1,403.97	$1,404.00	$1,404.00