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	$62.60	5.289%	$65.9109	$65.91	$65.90	$65.90
Purchase #2	$170.62	8.390%	$184.935	$184.94	$184.95	$184.90
Purchase #3	$59.31	9.336%	$64.8472	$64.85	$64.85	$64.80
Purchase #4	$84.25	10.213%	$92.8545	$92.85	$92.85	$92.90
Purchase #5	$88.82	6.533%	$94.6226	$94.62	$94.60	$94.60
Purchase #6	$65.86	8.265%	$71.3033	$71.30	$71.30	$71.30
Purchase #7	$102.65	13.392%	$116.3969	$116.40	$116.40	$116.40
7 purchase totals =	$634.11		$690.8704	$690.87	$690.85	$690.80