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	$199.98	8.183%	$216.3444	$216.34	$216.35	$216.30
Purchase #2	$210.55	13.539%	$239.0564	$239.06	$239.05	$239.10
Purchase #3	$110.37	7.174%	$118.2879	$118.29	$118.30	$118.30
Purchase #4	$208.45	13.447%	$236.4803	$236.48	$236.50	$236.50
Purchase #5	$165.60	10.702%	$183.3225	$183.32	$183.30	$183.30
Purchase #6	$35.86	13.305%	$40.6312	$40.63	$40.65	$40.60
Purchase #7	$148.91	11.743%	$166.3965	$166.40	$166.40	$166.40
7 purchase totals =	$1,079.72		$1,200.5192	$1,200.52	$1,200.55	$1,200.50