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	$169.48	10.569%	$187.3923	$187.39	$187.40	$187.40
Purchase #2	$79.28	6.362%	$84.3238	$84.32	$84.30	$84.30
Purchase #3	$156.88	4.843%	$164.4777	$164.48	$164.50	$164.50
Purchase #4	$63.59	10.782%	$70.4463	$70.45	$70.45	$70.40
Purchase #5	$127.39	11.674%	$142.2615	$142.26	$142.25	$142.30
Purchase #6	$20.88	3.626%	$21.6371	$21.64	$21.65	$21.60
Purchase #7	$82.87	3.585%	$85.8409	$85.84	$85.85	$85.80
7 purchase totals =	$700.37		$756.3796	$756.38	$756.40	$756.30