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	$152.90	7.415%	$164.2375	$164.24	$164.25	$164.20
Purchase #2	$171.64	5.717%	$181.4527	$181.45	$181.45	$181.50
Purchase #3	$17.96	13.546%	$20.3929	$20.39	$20.40	$20.40
Purchase #4	$77.44	7.791%	$83.4734	$83.47	$83.45	$83.50
Purchase #5	$171.60	13.273%	$194.3765	$194.38	$194.40	$194.40
Purchase #6	$217.60	4.480%	$227.3485	$227.35	$227.35	$227.30
Purchase #7	$39.47	7.260%	$42.3355	$42.34	$42.35	$42.30
7 purchase totals =	$848.61		$913.6170	$913.62	$913.65	$913.60