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	$75.43	9.794%	$82.8176	$82.82	$82.80	$82.80
Purchase #2	$62.32	12.868%	$70.3393	$70.34	$70.35	$70.30
Purchase #3	$57.83	13.557%	$65.67	$65.67	$65.65	$65.70
Purchase #4	$225.52	10.482%	$249.159	$249.16	$249.15	$249.20
Purchase #5	$195.30	11.526%	$217.8103	$217.81	$217.80	$217.80
Purchase #6	$212.47	10.205%	$234.1526	$234.15	$234.15	$234.20
Purchase #7	$92.50	9.836%	$101.5983	$101.60	$101.60	$101.60
7 purchase totals =	$921.37		$1,021.5471	$1,021.55	$1,021.50	$1,021.60