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	$192.81	3.773%	$200.0847	$200.08	$200.10	$200.10
Purchase #2	$104.28	4.157%	$108.6149	$108.61	$108.60	$108.60
Purchase #3	$73.66	13.456%	$83.5717	$83.57	$83.55	$83.60
Purchase #4	$120.31	13.163%	$136.1464	$136.15	$136.15	$136.10
Purchase #5	$120.64	6.354%	$128.3055	$128.31	$128.30	$128.30
Purchase #6	$160.32	3.241%	$165.516	$165.52	$165.50	$165.50
Purchase #7	$91.80	5.399%	$96.7563	$96.76	$96.75	$96.80
7 purchase totals =	$863.82		$918.9955	$919.00	$918.95	$919.00