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	$125.86	4.551%	$131.5879	$131.59	$131.60	$131.60
Purchase #2	$144.59	7.328%	$155.1856	$155.19	$155.20	$155.20
Purchase #3	$164.39	4.310%	$171.4752	$171.48	$171.50	$171.50
Purchase #4	$87.54	10.739%	$96.9409	$96.94	$96.95	$96.90
Purchase #5	$207.87	7.497%	$223.454	$223.45	$223.45	$223.50
Purchase #6	$183.97	12.223%	$206.4567	$206.46	$206.45	$206.50
Purchase #7	$96.25	6.282%	$102.2964	$102.30	$102.30	$102.30
7 purchase totals =	$1,010.47		$1,087.3967	$1,087.41	$1,087.45	$1,087.50