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	$180.42	3.827%	$187.3247	$187.32	$187.30	$187.30
Purchase #2	$134.35	5.688%	$141.9918	$141.99	$142.00	$142.00
Purchase #3	$243.69	9.509%	$266.8625	$266.86	$266.85	$266.90
Purchase #4	$89.58	11.128%	$99.5485	$99.55	$99.55	$99.50
Purchase #5	$74.82	11.332%	$83.2986	$83.30	$83.30	$83.30
Purchase #6	$235.75	4.277%	$245.833	$245.83	$245.85	$245.80
Purchase #7	$200.62	3.815%	$208.2737	$208.27	$208.25	$208.30
7 purchase totals =	$1,159.23		$1,233.1328	$1,233.12	$1,233.10	$1,233.10