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	$76.67	9.414%	$83.8877	$83.89	$83.90	$83.90
Purchase #2	$27.69	8.622%	$30.0774	$30.08	$30.10	$30.10
Purchase #3	$99.53	5.628%	$105.1315	$105.13	$105.15	$105.10
Purchase #4	$191.45	9.582%	$209.7947	$209.79	$209.80	$209.80
Purchase #5	$215.34	3.152%	$222.1275	$222.13	$222.15	$222.10
Purchase #6	$35.83	3.347%	$37.0292	$37.03	$37.05	$37.00
Purchase #7	$119.25	6.542%	$127.0513	$127.05	$127.05	$127.10
7 purchase totals =	$765.76		$815.0993	$815.10	$815.20	$815.10