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	$141.88	4.376%	$148.0887	$148.09	$148.10	$148.10
Purchase #2	$154.28	13.639%	$175.3222	$175.32	$175.30	$175.30
Purchase #3	$245.53	9.590%	$269.0763	$269.08	$269.10	$269.10
Purchase #4	$91.95	7.352%	$98.7102	$98.71	$98.70	$98.70
Purchase #5	$32.47	10.559%	$35.8985	$35.90	$35.90	$35.90
Purchase #6	$162.60	11.365%	$181.0795	$181.08	$181.10	$181.10
Purchase #7	$95.98	13.157%	$108.6081	$108.61	$108.60	$108.60
7 purchase totals =	$924.69		$1,016.7835	$1,016.79	$1,016.80	$1,016.80