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	$217.75	4.489%	$227.5248	$227.52	$227.50	$227.50
Purchase #2	$67.53	4.255%	$70.4034	$70.40	$70.40	$70.40
Purchase #3	$97.73	12.276%	$109.7273	$109.73	$109.75	$109.70
Purchase #4	$213.38	12.503%	$240.0589	$240.06	$240.05	$240.10
Purchase #5	$187.63	4.574%	$196.2122	$196.21	$196.20	$196.20
Purchase #6	$87.65	3.581%	$90.7887	$90.79	$90.80	$90.80
Purchase #7	$64.69	5.180%	$68.0409	$68.04	$68.05	$68.00
7 purchase totals =	$936.36		$1,002.7562	$1,002.75	$1,002.75	$1,002.70