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	$156.55	7.550%	$168.3695	$168.37	$168.35	$168.40
Purchase #2	$80.56	6.275%	$85.6151	$85.62	$85.60	$85.60
Purchase #3	$133.78	12.254%	$150.1734	$150.17	$150.15	$150.20
Purchase #4	$249.54	3.870%	$259.1972	$259.20	$259.20	$259.20
Purchase #5	$161.71	6.167%	$171.6827	$171.68	$171.70	$171.70
Purchase #6	$123.94	9.508%	$135.7242	$135.72	$135.70	$135.70
Purchase #7	$107.59	4.601%	$112.5402	$112.54	$112.55	$112.50
7 purchase totals =	$1,013.67		$1,083.3023	$1,083.30	$1,083.25	$1,083.30