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	$102.46	4.784%	$107.3617	$107.36	$107.35	$107.40
Purchase #2	$153.80	9.284%	$168.0788	$168.08	$168.10	$168.10
Purchase #3	$235.95	11.640%	$263.4146	$263.41	$263.40	$263.40
Purchase #4	$195.97	13.582%	$222.5866	$222.59	$222.60	$222.60
Purchase #5	$164.85	13.120%	$186.4783	$186.48	$186.50	$186.50
Purchase #6	$53.45	11.556%	$59.6267	$59.63	$59.65	$59.60
Purchase #7	$151.71	12.735%	$171.0303	$171.03	$171.05	$171.00
7 purchase totals =	$1,058.19		$1,178.5770	$1,178.58	$1,178.65	$1,178.60