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	$44.83	7.458%	$48.1734	$48.17	$48.15	$48.20
Purchase #2	$148.74	9.139%	$162.3333	$162.33	$162.35	$162.30
Purchase #3	$111.72	10.171%	$123.083	$123.08	$123.10	$123.10
Purchase #4	$14.96	12.803%	$16.8753	$16.88	$16.90	$16.90
Purchase #5	$104.27	5.481%	$109.985	$109.99	$110.00	$110.00
Purchase #6	$117.62	8.250%	$127.3237	$127.32	$127.30	$127.30
Purchase #7	$174.42	13.721%	$198.3522	$198.35	$198.35	$198.40
7 purchase totals =	$716.56		$786.1259	$786.12	$786.15	$786.20