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	$210.59	4.638%	$220.3572	$220.36	$220.35	$220.40
Purchase #2	$97.34	3.872%	$101.109	$101.11	$101.10	$101.10
Purchase #3	$196.54	7.296%	$210.8796	$210.88	$210.90	$210.90
Purchase #4	$79.37	8.137%	$85.8283	$85.83	$85.85	$85.80
Purchase #5	$168.88	7.404%	$181.3839	$181.38	$181.40	$181.40
Purchase #6	$28.72	8.595%	$31.1885	$31.19	$31.20	$31.20
Purchase #7	$163.72	13.347%	$185.5717	$185.57	$185.55	$185.60
7 purchase totals =	$945.16		$1,016.3182	$1,016.32	$1,016.35	$1,016.40