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	$104.90	13.426%	$118.9839	$118.98	$119.00	$119.00
Purchase #2	$52.89	9.435%	$57.8802	$57.88	$57.90	$57.90
Purchase #3	$154.46	4.154%	$160.8763	$160.88	$160.90	$160.90
Purchase #4	$163.39	12.114%	$183.1831	$183.18	$183.20	$183.20
Purchase #5	$114.88	7.859%	$123.9084	$123.91	$123.90	$123.90
Purchase #6	$197.96	6.626%	$211.0768	$211.08	$211.10	$211.10
Purchase #7	$185.92	5.589%	$196.3111	$196.31	$196.30	$196.30
7 purchase totals =	$974.40		$1,052.2198	$1,052.22	$1,052.30	$1,052.30