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	$140.44	9.608%	$153.9335	$153.93	$153.95	$153.90
Purchase #2	$137.71	13.166%	$155.8409	$155.84	$155.85	$155.80
Purchase #3	$43.30	4.476%	$45.2381	$45.24	$45.25	$45.20
Purchase #4	$27.93	13.285%	$31.6405	$31.64	$31.65	$31.60
Purchase #5	$238.27	7.117%	$255.2277	$255.23	$255.25	$255.20
Purchase #6	$239.49	12.258%	$268.8467	$268.85	$268.85	$268.80
Purchase #7	$27.53	13.172%	$31.1563	$31.16	$31.15	$31.20
7 purchase totals =	$854.67		$941.8837	$941.89	$941.95	$941.70