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	$89.52	9.334%	$97.8758	$97.88	$97.90	$97.90
Purchase #2	$241.81	6.245%	$256.911	$256.91	$256.90	$256.90
Purchase #3	$215.92	4.478%	$225.5889	$225.59	$225.60	$225.60
Purchase #4	$210.41	4.634%	$220.1604	$220.16	$220.15	$220.20
Purchase #5	$12.28	8.450%	$13.3177	$13.32	$13.30	$13.30
Purchase #6	$78.77	6.346%	$83.7687	$83.77	$83.75	$83.80
Purchase #7	$49.93	5.258%	$52.5553	$52.56	$52.55	$52.60
7 purchase totals =	$898.64		$950.1778	$950.19	$950.15	$950.30