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	$234.73	7.818%	$253.0812	$253.08	$253.10	$253.10
Purchase #2	$213.28	13.206%	$241.4458	$241.45	$241.45	$241.40
Purchase #3	$43.71	4.235%	$45.5611	$45.56	$45.55	$45.60
Purchase #4	$140.72	9.730%	$154.4121	$154.41	$154.40	$154.40
Purchase #5	$215.30	12.309%	$241.8013	$241.80	$241.80	$241.80
Purchase #6	$232.96	7.127%	$249.5631	$249.56	$249.55	$249.60
Purchase #7	$217.91	3.611%	$225.7787	$225.78	$225.80	$225.80
7 purchase totals =	$1,298.61		$1,411.6433	$1,411.64	$1,411.65	$1,411.70