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	$226.49	4.243%	$236.1	$236.10	$236.10	$236.10
Purchase #2	$146.97	4.524%	$153.6189	$153.62	$153.60	$153.60
Purchase #3	$67.32	13.171%	$76.1867	$76.19	$76.20	$76.20
Purchase #4	$103.49	5.611%	$109.2968	$109.30	$109.30	$109.30
Purchase #5	$238.53	6.736%	$254.5974	$254.60	$254.60	$254.60
Purchase #6	$125.69	13.349%	$142.4684	$142.47	$142.45	$142.50
Purchase #7	$161.59	10.190%	$178.056	$178.06	$178.05	$178.10
7 purchase totals =	$1,070.08		$1,150.3242	$1,150.34	$1,150.30	$1,150.40