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	$191.63	12.509%	$215.601	$215.60	$215.60	$215.60
Purchase #2	$20.69	5.763%	$21.8824	$21.88	$21.90	$21.90
Purchase #3	$71.43	3.104%	$73.6472	$73.65	$73.65	$73.60
Purchase #4	$97.65	3.165%	$100.7406	$100.74	$100.75	$100.70
Purchase #5	$131.92	10.710%	$146.0486	$146.05	$146.05	$146.00
Purchase #6	$118.53	7.109%	$126.9563	$126.96	$126.95	$127.00
Purchase #7	$134.36	13.312%	$152.246	$152.25	$152.25	$152.20
7 purchase totals =	$766.21		$837.1221	$837.13	$837.15	$837.00