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	$168.50	11.444%	$187.7831	$187.78	$187.80	$187.80
Purchase #2	$90.97	6.134%	$96.5501	$96.55	$96.55	$96.60
Purchase #3	$178.45	6.172%	$189.4639	$189.46	$189.45	$189.50
Purchase #4	$101.57	4.177%	$105.8126	$105.81	$105.80	$105.80
Purchase #5	$125.71	13.463%	$142.6343	$142.63	$142.65	$142.60
Purchase #6	$77.83	12.160%	$87.2941	$87.29	$87.30	$87.30
Purchase #7	$63.73	5.704%	$67.3652	$67.37	$67.35	$67.40
7 purchase totals =	$806.76		$876.9033	$876.89	$876.90	$877.00